cute little guy. Love the bouncyness of it
The arms looked off because you only did half a walk cycle. You colored your legs differently, see how it jumps after one cycle?
To get a full cycle just duplicate your frames and swap fore and background (basically)
Then you can have the full arm swing motion too
In terms of readability, i bumped up the brightness a bunch. yours does currently look like a black sprite with brown hands and face.
edit: woe is me. i actually derped and the arms swing same as the legs. flip that around, or it might look derped