The head looks good, I would just add a more appealing facial expression. He's a bit neutral. Especially the mouth.
What stuck out to me are his feet and arms.
sideview: look at the front foot on x1. I think it's too high up. The walk is very casual so having the foot rotated that high up feels unnatural, same with the toes pointed up like that. Don't go higher than what you have at x2.
The steps also feel slow from x24 to 1 and 2. I think it's mostly how little the foot goes back from x1 to x2, but big again to x3.
Same with the other foot from x24 to x1, there's suddenly a smaller distance that the foot travels spacing wise. Then still small spacing from x1 to x2, then a big one to x3. So that slowdown and that pop gives the walk a weird feeling. When you watch it looped you sense a pause and then a pop.
Also watch the arc of the foot as it lifts off the ground. Track the heel for instance. From x2 to x3 it goes up in Y a lot, then a little from x3 to x4 and then a sudden drop from x4 to x5. If you reduce the height on x3 and lower it a bit on x4 you'll get a nicer arc going into x5.
You can also lower the foot on x9 and x21. With a relaxed walk like that you can have the feet almost graze the ground.
The other thing, when looking at the front view, it looks like the feet vibrate. Make sure that they are locked on the ground, no wiggling.
Now the arms. They feel very straight, same with the hands/fingers. I would reduce the amount the arms swing in (frontview) and don't rotate the hand as much during the back swing (again in frontview at x12 for instance, rotate the hand (screen left one) so that you don't see as much of the palm).
Rotate the thumb away from the hand in order to give it a more natural pose. Right now the hand/finger pose reminds me of a military salute where everything is straight.
What accentuates that salute feel are the straight arms during the swings. Look at the sideview, x7. The arm is pretty much straight and the wrist is bent too far back, so reduce the amount of back rotation for both hands and bend the arms so that they look more like what you have on x23.
Give the fingers are more relaxed feeling.
Picky picky! :) Looking good though!
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26 minutes ago