Overlaping and making lines

Hi, I'm trying to make something but I can't seem to figure how to overlap and image with a background.

Let's see if I can explain mysself...

I have a background and I have an image that I want to put over the background but in a way so that the corners don't match.

I can't find a good image to put as an example but I made this with paint, it's very basic but I hope it could help you understand what I want.

Okay, one problem solved, I just had to save to web or something like that. (My program is in spanish).

One more problem, how cant I put a shadow to the picture but just on the side that is above the back ground??



And one more thing, how can I make a line between two images???