I'm a terrible artist, but as with most drawing games, I think that might actually make it more fun.
I'd love a fill function. I'd also love to be able to pick a color from the ones already used in the picture. (Using the color picker changes the palette, so if I change a color I've used, I can't seem to match it exactly anymore.) But I can understand why you'd want to keep the tools simple, so I can't take a point off for that.
More words would be nice. I haven't been playing long, but I've already seen GAMEBOY three times. I won't take a point off for that either, because the latest news says more words are coming.
Excellent choice of music! Overall, a simple but nice drawing game.