You have to work on your shading. I'm not talking about Gradients or Filters here, mind you. I mean actually taking the layer and manually shade the hell out of it. If it serves as any advice, take a separate layer (on Multiply), use the Polygonal Lasso tool to rope in the areas you want colour in, and start shading it. If you want richer colours, use about five different shades.As is, your work (especially in the last one) is rather untidy. White specks all over the outlines are a definite no-no. Also, wean yourself off of filters and gradients. Those are bonuses, not your tools of the trade. If you want to make some real progress, LEARN THESE WELL.- Blur Tool- Smudge Tool- Polygonal Lasso Tool- The Hardness/Thickness settings on your Brush ToolHate to sound harsh, but filters and gradients are NOT impressive. It's a cheap shortcut.You want real results, follow my advice. You won't be sorry.
Its better to learn the pen tool over the lasso tool. It took me years to figure that mc thing out, but damn is it worth it