Tutorial for spicing up B&W images
from
to 
Program: Photoshop CS4
Difficulty: Easy, basic knowledge (e.g. how to sharpen, merge layers) assumed
Translatable: Yes, as far as I know
PSD Included: No
This is my first tutorial so forgive me if I do something wrong or don't explain well enough. I myself prefer tutorials with less direct instructions (by direct I mean e.g. "fill with #fff666") where you have more power to modify the result and effect according the base you're using (e.g. "fill with lemon yellow"). So that's what I'm going for here as well.
1. Select and prepare your base.
This works best with strong contrasted images and better yet, if the skin is light. My base has colors, but this step works for B&W as well.
After sharpening my base looked like this (well not exactly, I have already deleted the base but this is almost similar crop from the original image):

There's really nothing too wrong with it, but let's brighten it up a bit.
I used a trick I learned somewhere in this community (raise your hand if you want credit!): Duplicate your base, set the copy to Screen and lower the opacity to somewhere around 50%. Then duplicate the Screen layer twice (or thrice or how many times necessary), leave the first copy to Screen and set the third, uppermost layer to Soft Light. Change the opacity till your base looks good. Especially with B&W icons I usually add a Gaussian Blur filter of a low radius (e.g. 3-5) to the soft light layer, it gives the icon a nice soft look without looking too retouched.
This is what I have so far.

2. Merge all layers. This just because I like to have as few layers as possible (since I usually have A LOT).
3. Make it B&W (if it isn't already, obviously).
As with almost anything, there are many ways to do this. You can simply desaturate the image by U + shift + cmd (ctrl in Windows). If you do this, the result looks like this:

I, however, usually do it with a black and white Gradient Map. To do this, first press 'D' to change your colors to black and white (black as Foreground Color). Then select Gradient Map from the Adjustments tab. You should have the right one from the start, but if not, choose the first one called "Foreground to Background". Now you can also edit the Gradient to adjust to your image.
This way you achieve a less flat and definitely more interesting look than by simply desaturating:

Way better, right?
4. Again, merge the layers and delete what you don't need. Or keep them, if you want to.
5. Choose a texture and paste it to the document beneath the original image (Mila Kunis here)
This is where the rich opportunities of this technique come from. Your 'texture' can be just anything, and every pic you use here leads to a different result. Just make sure the colors aren't too light. I used a photo I took last summer, resized it and desaturated it. This is what the part that's on the icon looks like:

The advantage of using big photos is that you can move them around and look for the perfect place to put it. At first (if you happen to have a piece of sky in your 100x100) it may look like nothing but when you play around with it, you can end up with some really nifty effects.
I've done a lot of edits like this with pics of plants, they have such nice texture.
There's no need to desaturate the picture either, but with what I'm going to do later, it looks best desaturated.
6. Set the top layer to Lighten. To make it a bit clearer:

You do achieve the exactly same effect if you put the texture layer on top and set it to Lighten instead. But, assuming your top layer is ready and perfect as it is, it's easier to modify the texture when it's at the bottom. Now, if your icon looks too bright, you can easily duplicate the texture layer and set to Multiply to make it darker. Or you can fix contrast, sharpness or whatever needs to be done. This is what I've got:

This is where the contrast and brightness of the original base matter. If the face'd have been darker, it wouldn't stand out as clearly.
7. Leave it as it is or add some effects. Here the best textures are the ones with dark background and moderate-in-lightness (what a monster of a word) colors. I used one of my own, it's kinda crappy so I'm not going to share it (I'm 1000% sure you can find a similar one just anywhere). Anyway, set whatever you chose to Lighten. (I guess you could use Screen Layer as well, but I prefer Lighten.)
Ta dah!

Ain't it just pretty?
Other icons done with the same method:

Program: Photoshop CS4
Difficulty: Easy, basic knowledge (e.g. how to sharpen, merge layers) assumed
Translatable: Yes, as far as I know
PSD Included: No
This is my first tutorial so forgive me if I do something wrong or don't explain well enough. I myself prefer tutorials with less direct instructions (by direct I mean e.g. "fill with #fff666") where you have more power to modify the result and effect according the base you're using (e.g. "fill with lemon yellow"). So that's what I'm going for here as well.
1. Select and prepare your base.
This works best with strong contrasted images and better yet, if the skin is light. My base has colors, but this step works for B&W as well.
After sharpening my base looked like this (well not exactly, I have already deleted the base but this is almost similar crop from the original image):
There's really nothing too wrong with it, but let's brighten it up a bit.
I used a trick I learned somewhere in this community (raise your hand if you want credit!): Duplicate your base, set the copy to Screen and lower the opacity to somewhere around 50%. Then duplicate the Screen layer twice (or thrice or how many times necessary), leave the first copy to Screen and set the third, uppermost layer to Soft Light. Change the opacity till your base looks good. Especially with B&W icons I usually add a Gaussian Blur filter of a low radius (e.g. 3-5) to the soft light layer, it gives the icon a nice soft look without looking too retouched.
This is what I have so far.
2. Merge all layers. This just because I like to have as few layers as possible (since I usually have A LOT).
3. Make it B&W (if it isn't already, obviously).
As with almost anything, there are many ways to do this. You can simply desaturate the image by U + shift + cmd (ctrl in Windows). If you do this, the result looks like this:
I, however, usually do it with a black and white Gradient Map. To do this, first press 'D' to change your colors to black and white (black as Foreground Color). Then select Gradient Map from the Adjustments tab. You should have the right one from the start, but if not, choose the first one called "Foreground to Background". Now you can also edit the Gradient to adjust to your image.
This way you achieve a less flat and definitely more interesting look than by simply desaturating:
Way better, right?
4. Again, merge the layers and delete what you don't need. Or keep them, if you want to.
5. Choose a texture and paste it to the document beneath the original image (Mila Kunis here)
This is where the rich opportunities of this technique come from. Your 'texture' can be just anything, and every pic you use here leads to a different result. Just make sure the colors aren't too light. I used a photo I took last summer, resized it and desaturated it. This is what the part that's on the icon looks like:
The advantage of using big photos is that you can move them around and look for the perfect place to put it. At first (if you happen to have a piece of sky in your 100x100) it may look like nothing but when you play around with it, you can end up with some really nifty effects.
I've done a lot of edits like this with pics of plants, they have such nice texture.
There's no need to desaturate the picture either, but with what I'm going to do later, it looks best desaturated.
6. Set the top layer to Lighten. To make it a bit clearer:
You do achieve the exactly same effect if you put the texture layer on top and set it to Lighten instead. But, assuming your top layer is ready and perfect as it is, it's easier to modify the texture when it's at the bottom. Now, if your icon looks too bright, you can easily duplicate the texture layer and set to Multiply to make it darker. Or you can fix contrast, sharpness or whatever needs to be done. This is what I've got:
This is where the contrast and brightness of the original base matter. If the face'd have been darker, it wouldn't stand out as clearly.
7. Leave it as it is or add some effects. Here the best textures are the ones with dark background and moderate-in-lightness (what a monster of a word) colors. I used one of my own, it's kinda crappy so I'm not going to share it (I'm 1000% sure you can find a similar one just anywhere). Anyway, set whatever you chose to Lighten. (I guess you could use Screen Layer as well, but I prefer Lighten.)
Ta dah!
Ain't it just pretty?
Other icons done with the same method:
