I found this small, crappy quality image:
[img]http://img41.imageshack.us/img41/4905/1256846438711.jpg[/img]
And vectored the silhouettes. Then I replaced the background:
[img]http://img18.imageshack.us/img18/2097/ninjaturtlesa.png[/img]
But I still don't know how I feel about the background. I feel like I could do something better with it - maybe something more abstract, or more green to make it turtley.
Here are the silhouettes alone if you want to mess around with it. I can post the SVG too if anyone wants that.
[img]http://img41.imageshack.us/img41/148/ninjaturtles.png[/img]