Not sure how you got that texture on the planet, but I agree it looks a
bit cartoony. As described in alyn's planet tutorial, take textures from different
places, clone parts, add more textures, play with blending modes, erase parts,
untill you get a nice looking textureIt takes time, I know, but it's worth it.
If you want to learn how to do a nebula better, Alyn also made a nebula
article, where he included links to a couple of nebula tutorials.
How did you do the shadow on the planet? If you copy the selection of the
planet, then make a new layer, make it black it with black and then do
filter-> Gaussian Blur, you would get a better shadow. Lower the opacity on
the layer a bit to get a similiar effect to what you have now.
The stars, seems a bit repetitive as HostilePenguin said. Check out this tutorial
made by Greg Martin, where he describes how to do a realistic star field.
Good work though, you are getting better!![]()