Icons from cartoons

This isn't a question about making animated icons, but I was wondering if anyone has any good tips for making an icon out of a cartoon picture? For example, I wanted to use some caps from Alice in Wonderland to make icons, but I'm really used to working with photos. Cartoons seem to be really hard to do some effects on. And plain, I don't think it looks very good. Does anyone have any helpful hints? Thank you!