Cool work dude
Some things I notice at first glance:
Blonde hair doesn't need a black outline IMO especially inside the sprite and even more especially in the highlighted yellow areas. You could use your existing varying shades brown etc. or something instead to balance out the contrast.
Seems like he's leaning back a bit making him unbalanced. Maybe bring the whole top section from the knees and pelvis forward, and adjust the bottom of legs to compensate. This should allow his torso to still lean back but balance him so he doesn't fall backwards.
The feet seem a bit TOO big, almost hobbit-like, in that no other body parts match their proportion.
I'd say reducing the foot size is the easiest solution, otherwise u gotta make head and hands etc. bigger and I don't think he'll look as good that way.
Feels to me like shield could come down and right a bit to balance and space out the composition a bit.
Feels a bit cramped where it is.
Something abourt the face seems like its too washed out. Since its typically the primary focal point, you could use higher saturation and contrast here.
PERHAPS there's a way to combine 2 different shades to give a similar overall appearance but with much more vibrancy and priority. I don't know how this works but I'd be really interested to find out...something like how 2 or 3 contrasting colours of varying saturations can be clustered against each other to give the appearance of balancing out to a chosen colour...perhaps paint mixing and print colour mixing theory applies here