It would be really cool if we could edit the screen that pops up when people click the "Download" button on a game. Especially if we'd like to let them know something specific on there like "If you donate now, you'll get the game free later when it launches on Steam." and stuff like that.

Also particularly I'd like to bold the text "This game is free" on that popup because people click it and then think they have to pay the Suggested price and just close the whole page.