It would be helpful to know what style you're going for here.
The tree looks very cartoonish, as if made of clay or plastic. I can tell you that the bright stuff at the pointy ends should be a couple of pixels above their current position.
The trunk of the tree looks as if a flashlight has been pointed to it: Leave the the darkest shade for the upper part, and the middle shade for the rest of the tree. I'd hesitate to use the brightest shade. Ask yourself: Is the sunlight reaching the trunk directly?
Also, you should modify the base of the tree to match the topdown view of RPG Maker VX.
The brick wall doesn't have a clear light source. Assuming it's outdoors sunlight, make the upper part of the bricks lighter ...but not too much: the pattern will repeat on every single brick, and a wide range of shades wouldn't look good. You should also make the small dots on the bricks (the texture) brighter, so they don't conflict too much with the general view of the bricks.
In the Shrubling, you should avoid using black on the eye outlines and mouth. Maybe use a very dark green instead, just like in the outline of the body. As you might know, it's a rule of thumb to usually avoid pure black, because it rarely manifests itself in nature (at least, in daylight. Things like black hair are actually a very dark shade of color, not black.)
Also, maybe the eyes should be a more saturated color, to stand out more (maybe it's the black eye outlines, that make them less prevalent)