Your main problem at the moment is the things that Pixelaro stated that you failed to acknowledge.
I've made a quick, sloppy edit to point out what I mean and what's been bugging me personally.
The angle of everything is off. As you have it, it looks as if he's standing sideways on a hill going upwards or something to that effect. If that's the case, then brush should be positioned at about the same height (or higher) than his right foot (our left). This can be fixed by either changing the positioning of the brush or bringing everything to the same plane, as in my second edit. In that case, you might have to change the feet to being more flat, but still.
I'd also like to say I'm no master at folds, but the bandanna seems kind of bland. You could easily add some folds in it and such.
The brush is nice, but it's bland as well. Don't be afraid to add an extra shade and give things a swirly texture, as his paintbrush actually has.
His left arm is positioned behind his leg. That's just kind of odd. Imagine standing at an angle where people couldn't see your hand because it was being covered by your leg. Odd, huh? This could be easily fixed by just drawing the hand in front of him.
I'll have to say you're doing alright, CoolYoshi. The shading is nice and the colors are effective. Don't be afraid to go outside the box!
-Dex