<- vs ->
A small edit to help you identifying/tackling your picture weaknesses.
1) be consistent with lightning. This is blatant on the ladder where the extremities are both lit. Assuming a cylindrical shape for the vertical staffs, both staffs should have their higlight on the same side, and their shadow on the same side, because they receive light from the same place. Watch out when flipping things, thus, because you might end up with contradictory light sources. This is the case with your flowers.
2) shading convey volume. look at your flower and at your character's hair. The way you placed highlight and shadow says "think of me as of a cut-out cookie : I'm an extruded flat thing". I tried to alter your leftmost flower to show how you can place the highlight at the part of the object that receive most of the light.
3) organic stuffs don't have straight color ramps. Only plastic will have shadow that have the same hue for mid-tones, highlight and shadows. Leaves, Hairs, flowers, etc. tend to introduce a hue shift in the color they reproduce, for various reasons (ambient lightning, etc.) The sun is yellow, the sky is blue -- that's an ulitmate application of those principles. As a basic guideline, you can almost always tweak your highlights towards yellow and your shadows towards purple/blue. It will require trials to find the proper tone, though. I overdid it a bit.
4) exploit contrast to enhance readability of your game: the face of your character is the most important thing in your game. It needs to pop out. pale blue eyes reaaly don't help on this. I also toned down the hihlight of your ground, which are heavily geometric and could therefore attract undue attention on them. I also gave your character's belly some volume with additional shading, but it's still bleeding to much into the tree. My edit suffers a problem with the new shadows for bushes and tree here : they should be toned down (most likely, the saturation should be reduced) as they are now the most contrasted things.
5) take care of your lines Sometimes it's called banding, sometimes it's called jagginess. the fact is, on a computer screen, a single misplaced pixel can ruin the smoothness of a curve. And properly placed AA pixels can greatly improve it. The mouth, and the hair of your character suffer alot of it. I'd suggest you focus on that first, and keep working only on your character until you've got something satisfying. Observe tool-rendered circles, and the progression they use. If necessary, draw your character on a millimeter-sheet and hatch the squares where your pencil has crossed the square.
HTH.
Oh, and btw, the grass doesn't stick out like that. I suggest you drop the vertical lines altogether and only add some bumps of pale green for now.
I'd also suggest that you look for something else than tetris blocks for your ground: the rest of your art is strongly curved and that introduces a mismatch in the styles that breaks the "believability" of your world. I.E. people can accept Yoshi's Island art because it looks like
all the world is made of crayon strokes. Bring in a SGI-rendered barrel from Donkey Kong Country there, and the magic stops working.
edit I realise afterwards that I've overlooked your previous posts: your lightsource is obviously on the right, and I edited the flower and the ladder as if it was coming from the left
