Yea! I love your attitude. Someone who really wants to improve always will improve! and keep in mind my advice or suggestion does not take away from how awesome this concept is, it would only improve it.
So, look at objects in real life and notice that almost nothing has a hard black edge around it. Cartoons look flat because of those thick cartoony black lines. In your case here, it's that black around the edge of your character design that is making it look flat. Contrast is important but black thick edges flatten your design.
When we look around we see a lot of reflected light. Light bounces off stuff and hits other stuff constantly.
Copy and paste that link. Notice how the ball has a core shadow - and just after that the edge is slightly lighter - that's light bouncing off the floor which is hitting the ball. So if you want something to pop out of your page and look more dimensional start drawing and thinking about light.
Also - Look at your hand right now. Notice how it's actually light around the very edge of it, then as you look more in toward your hand it gets darker then lighter again. Skin is cool because light penetrates the layers but the way light hits objects is universal.
So yea, apply that core shadow and reflected light. Try drawing that ball and stretching it into an oval then shading it. In this case don't put thick black lines around your object - unless it's a cartoon or technical illustration - or maybe you want a heavier line weight to draw your eye to an area on the image.
basically if you want 3 D - no black thick black lines.
also remember when things are super shiny, or glossy they have sharp highlights - look at anything shiny in your room - notice the hard white light reflecting off of it. So for example - if your character has wet toes, or his skin is smooth there, make a light sharp highlight on the lightest areas of his toes and it will look like the light is bouncing off a glossy or more reflective surface.
and see that highlight in his yes, that white spot you added is reflected light. Eyeballs are so glossy that you get a sharp white reflection, or little white circle on the eye. It's just light bouncing off the glossy surface of the eyeball. That's why your characters eyes look more real, and "life" like.
Super awesome man! I can't thank you enough for the advice. I am going to give it a go tonight and see what I come up with and really try to give this character a more 3d look. I will eliminate the thick black edges where light is hitting and keep the darker areas where light isn't. I have done the sphere/egg studies before but it always seemed so much more simple than dealing with a complex object or character. Eyes always seemed easier, I think because I understand more about how the light reflects off them. I will put your advice to good use! Let me know what you think when I post the more refined version!