It would be really nice if there was a way to modify a picture without having to delete it and re-upload it (and therefore lose all votes). If only a minor change has been made to the picture (for example, a dust spot was photoshopped out), it seems silly to have the picture go through all the voting process again.

Perhaps, the modification could be reviewed by someone, and if they deem it to be minor enough, then all votes are retained. Otherwise, all the votes are deleted, just as if the image had been deleted and re-uploaded.