Background is a 3D render, and not usable. Please read 5.7. 3D Renders or Illustrations as Source: Using other people's 3D renders or illustrations (even with permission and no matter in which form they are offered) creates a false impression of your artwork. So 3D renders or illustrations (this includes brushes, tubes, clipart, pdf files) can not be used as sources, unless they are entirely created by yourself.

Now all you have to do is remove the shadow of the vulture, since you've got the light source directly overhead, and it's far behind it, which would cast no shadow. GL author.