you over all rendering needs a little work.
- better define the form with high lights - lightest lites against darkest darks
- give some dept to the stitching - using the deboss tool is PS is a qucik simple way or if you are using sketch book pro create a custom brush
- draw in form lines on a separate layer to help you visualize where you want your highlights and shadow
use reference material, here is a quick one i found that will help steer you in a direction
also don’t just have ref. samples of other people renderings in front of you have images or actual samples of the materials in front of you as well. Study and duplicate what you see.
