So, in general, your grasp on anatomy is serviceable, it isn't your biggest weakness.
The biggest problem with your work is a lack of really solid structure behind the forms. You seem to be trying to strike this weird middleground between cell-shading and formal rendering. By which I mean, you're trying to let the colors and shadows define where the forms end, but at the same time, you're still using these wispy sketchy lines to outline them. The consequence is that neither is being used to its fullest potential, and it's making the pieces look unfinished, like you accidentally left your sketch layer on. The girl in the military regalia is the most appealing thing you posted, and that's due in large part to the fact that you've used very deliberate strokes for the outlines and shading, with virtually none of the sketchiness seen in your other pieces.
Since you also seem to be trying your hand at more thorough rendering, as seen in the non-Pony DnD image, I'm going to assume you're also interested in using light and shadow beyond simple cell-shading, so I'm going to recommend you read this. It's got a lot of good pointers on how to make your forms much more solid, and the artist is a lot better at explaining and illustrating their points than I am.