Okay well that makes sense. There is no way to delete photos after a user is deleted.
You can try inputting this url in your browser with your site name of course etc and change the userid to the userid of that deleted user to see if it deletes his photos. This is the url format used in a users profile where the admin can delete all there photos
http://www.yoursite.com/gallery/adm-...lphotos&uid=49