Current WIP (9th)
no offense but... meh.... You're using a hard round brush all the time, doesn't look that good
example
If you're trying for realism you'll need more shading and less hard lines. It greatly helps if you have a reference, so find some images of the closest thing to the creature you're creating, and attempt to mimic the shading of the image in your own.
I'm no pro, but this was my attempt at realism.
example
Pay attention to the softness, hard lines are important, but not as important as settle differences in shading.