Not really pixelart at all and this happens to be a pixelart forum.
It's very messy. Cleaning it up would really benefit readability. A lot of the colors are almost the same colors as others.http://pixeljoint.com/pixelart/50243.htm An example of graffiti with 10 colors, strong design and a very clean look. Even thought it's kind of grungey it's clean. Look into it.
Oh hum, looks better now, with the non-jpgness and all. It looked like you just used paint and scribbled some purple over white. It doesn't look like that anymore. You might wanna add some AA on the writing though, to make it look more in place iwth the moon and such.