When you've developed it a bit more, make sure that in between the click from art profile to evolve an image, there is something other than a sign-up form. You need to show the potential to new users before they will sign-up. As it is now, the majority would see the sign-up and walk away.

Make sure your example derivative is really convincing. Not sure if your market is professionals (who might do this in Lightroom or Aperture), groups (wanting to share professional derivatives privately) or people creating lolcats and so on, but your example for each case should be quite different.

I already applied your suggestion for art submitting/evolving page, I can definitely see it attracting more people that way by showing the guts.

Really appreciate your input! :)