As of June 30th, Brawl is no longer accepting anything User-generated. This includes screenshots, replays, and custom stages. Why? I'm not so sure. Details were not given. Here is what Smash Bros Dojo (The Official Smash Bros. Brawl Website) posted as a notice:
As of June 30th, 2009, we are no longer accepting user-generated snapshots, stage designs, and replay data. Thank you for all your posts! Please note that the distribution service will still continue.
Target Smash!! and Home-Run Contest world records will be updated soon!
Here's the link to the website if you want to be certain that what I'm saying is true. But why would you go there for that reason? Would I lie to you, of all people?