Given the amount of work here and how much you have learn I'd suggest calling it done and start on something new.
At the very least take a two month break from this one and look at it with a fresh pair of eyes then.
Things I recommend for the next project/scene.
Decide on a firm standard for how the scene will be made.
Examples:
1. Simply shapes and colors fills no shade no outlines.
2. Simply shapes and color fills with black outlines and no shade/shadows.
3. Painted images imported as png.
4. Shapes, flat shade/shadows and color with black outlines.
5. Shapes, flat shade/shadows and color with color outlines.
6. Textured shapes no outlines.
7. Textured shapes with outlines.
etc etc
Since you are learning I'd recommend sticking with 1 or 2 to begin with. These will help you get the hardest part done, the design and layout. It will also be the easiest to tweak.
Do several scene this way and see how you will be better and better with practice.
Once you've done a good amount then you can go back the the basic versions, make tweaks as needed and then if you want start adding more flavor such as shadows and lighting.
With lighting again, start with the basics. Use flat lighting, no blur in the shade or shadows.
During all of this I recommend you do some pencil drawings of still life. But keep it simple. An egg in a white bowl on a white plate. Study how the light and shadows are cast. It may sound dull but I have some awesome drawings from studies like this and it helped me understand lighting better this way.
Also look at other people's art and see what works well. Take Parker's back grounds for instance. He has done a lot of backgrounds and many of them are very basic with shapes, color and a little bit of texture. If the design is good you can do a lot with very little.
http://www.coroflot.com/public/individu ... lty=12&c=1&