Note: replying to Commons-L as I am not on Foundation-L.
Hi -- I'm one of the WMF staff programmers working on Commons Usability. And by "one of", I mean "the". ;)
Reiterating arguments I made at the Village Pump, I'd like to note on this list that in my professional opinion, this would be a step backwards for usability.
http://commons.wikimedia.org/wiki/Commons:Village_pump#An_initial_notice_to_...
If you feel that the purpose of Commons is not obvious to visitors, I suggest a tagline that appears at the top of every page.
http://www.useit.com/alertbox/20010722.html
My suggestion would be something like "A vast library of educational images, movies, and sounds that anyone can use or contribute to."