Wikimedia commons is urged have a site where everyone can do a query reagrding the possibility and needs of an Upload with just a URl (like this for example):
Output should state wether a file given within the URL matchs a file that already is on commons or already was asked before ( giving possible notices if this work is uploadable or (why) not.
The match has to be checked 1.) by direct file-compare 2.) by a file-compare like tineye and google, providing possible matches (at least) within the files already on commons.