I think it might be nice to have a tiny resource library built into the editor.
A collection of generic game items, sound and a font.
Graphics:
Ball, spaceship, star, man, rectangle, square, coin, skull, key..
Sound:
Beep.
Font:
A simple font.
Why?
Sometimes I want to experiment with an idea but I don't want to have to set up graphics, sound etc.
Often it is more important to set up the dynamics of a game and then do the eye-candy later when the game works.
It would also be handy for quick demos!