If you didn't want to go back and ajust the head bob, you could simply edit the title of the piece to "Limping Jack!" :p  Nice colour choices, and the design is quite cute...

I agree with milkyjon 100%, and I think one thing that would help even further would be to make his head bob not once in the cycle but twice, as each foot comes directly under him, pushing him upward. The one head bob you have is perfect, so it would just be the same thing again when the other leg moves under him. That way his head is up half the time and down half the time.

Sorry for the double post...but I thought id appoligise for calling you jack, when its the sprites name. Doah

Hey Jack, I think this is nice, smooth action and nice design. It looks as tho he might be doing a bit of a moonwalk tho. His legs slide back and forth on his toes, keeping contact with the ground. The way I always do walk cycles (or any animation for that matter) is to jus sketch in some rough blobs for feet one colour for each foot and then have them going round in a circular motion, in the air for half and slideing back along the ground for half of the time. They must be doing the same animation as each other tho, and travel the exact same height and distance or it looks odd. Once im happy with the rough blobs going round then I fill in detail. cut the animation one pixel shorter for weight impact when each foot hits the ground for added weight (Youve done that here but on one foot.). And give the shoulders and head a pixel rotation  on each ground contact in opposite direction for extra depth and a 3d look. I think the character is great tho so itd be worth the effort tweeking the cycle a bit.