A million levels... isn't that too much noise? I don't know how LBP downloading center works, but I guess I would download the best rated ones, leaving little room for the newest and not so newest additions.

You can search by word, search by tags (people can put certain tags (description words) on levels, top 3 or so are that levels tags), top ranked of course, there is also a way to search randomly by just skipping to different LBP earths. I was always able to find some pretty diverse stuff on there, but every time I created a level it only got from 0-5 plays by people. That takes your motivation away to create when no one plays your stuff. My best is probably a classic donkey kong level called "Donkey Kong Classic" I believe. try it out.

That is what I meant, unless you get a community behind the map to test and rate it enough, your effort may be very well overlooked. Maybe they should receive maps, choose the best ones, and release them as a map pack for everyone, letting you share maps with friends but not the community unless it is accepted as a part of the map pack.