That was an attempt to keep the puffiness of his onesie intact. Skeletons can be hard to make cute but the blue onesie is probably the biggest factor selling the kiddishness of the design!

Some minor edits! That extra shade on the front of the hood wasn't quite working, and the face didn't really scream "skeleton" out so I gave him a more skeletal head.
I also changed up the form a bit, giving him more of a poofy look, and made it so his ankles turn to match his crouch!
In addition to that, I fixed his arm so it moves up instead of extending outwards like a stretch armstrong toy!

I also added those dark divider lines you put on his leftmost art on the rest of his limbs and around his neck!
There's more you can probably do here but hopefully this sets you in the right direction!

Well, first thing I'm noticing is that the wings look way too segmented.
Here, a guide on how wings are structured:


You could fix what you have now somewhat though by simply making the top edge more solid to give it a more structured look.

On non-wing related stuff, her hair kinda billows out too much and gives her head an inflated appearance, i'm not sure if that's what you were going for but notable nonetheless.
The hands are also too small, and contrast pretty hard with the otherwise-realistic proportions. Don't cut things off at the wrist, and try to add those fingers and thumbs.
Finally, the feet need a lot of work. If you need a good guide, try to think of them primarily as basic shapes to simplify the process of drawing them.
Like so, this is a bit of a rough example but the method I use is I start with a ball then add two triangles and a square for the toes. The back triangle I then round out a bit, and I have a side foot.
The front is mostly the same too, I just add more squares and eliminate that second triangle!

This is a great method for simplified art styles, breaking things down into basic shapes like this has made a lot of things easier for me and it's a good habit to keep around for complicated bodyparts like feet or those horrible mutant flesh-spiders on our wrists we call hands.

The effort you put in really does show, though, so kudos for that! Keep going!

CFKaligula's edit fixed the problem I mentioned with the color scheme, the more earthy tones sell me far better on the forest part than those sandstony colors did. The darks on the tree trunks look a bit off now though, so it might be worth it to try tweaking that some