We usually do .gif or .jpg, but Jedi does his in .png and we've had no problems with them (I think most systems/programs are compatible with .png nowadays). As long as the screenshots are the same size as the standard screenshots, we won't care (see the site if you don't know what the standard size is).
Whenever you've got them ready, compress/zip the file and send it to me. Thanks, man.
I'm taking 3 pictures of each one the title then 2 others showing gameplay. Also I'm doing 4 letters which are K,L,M,N if no one has gotten them.