Have you checked the apparently-corrupted images with multiple programs? Maybe it's a bug with the program you're using to view them. (I'm assuming by "image" you mean a picture, not a disk image, but the question applies either way.)
Another thing you could try is to perform a checksum on the files as downloaded using eMule and using aMule and compare them. You can use the "alcc" program (part of the aMule package) to generate the ed2k file hash for the file and see if it matches the hash from the original link (or search result) you used.