Alright, I'm gonna try and give a full-out critique on this. I'll admit--I'm not the best artist out there. But there are a few tips that I feel you could really use.
For the chibi:
-always keep shoulder level on the same line.
-clearly mark where the shoulder ends and the arm begins
-for the ears, make it clear whether the ears are facing front or the side
-try not to draw the legs closed together, its a really stiff pose
-pretty good anatomy for the most part.
For the headshot:
-use proper guidlines and anatomy. Look up tutorials and observe their anatomical structure
-The neck is too thick
-Eyes are improperly spaced
-Forehead is too small
-Hairline begins too close to the forehead
-Does not show the full ear, it looks like its plastered on.
-Background is nice, coloring is good.
Above all, remember to have fun and enjoy yourself <3