Here are my suggestions (Organized)
I think that users with a certain amount of rep should get their own small little blog.
When the multiplayer feature comes out, I think there should be a MMO section of the arcade.
A search bar.
Develop games in your browser. Powerful, performant & highly capable.
... when multiplayer feature comes out Arcade will be filled with another thousands of modified "games" from C2\Examples folder.