seems a bit fast honestly and overall jumpy; i think generally with things like this its nearly impossible to make it smooth without multiple sprites like what sonic 2 did for the final boss
if you are working by general snes limitations, the current animation you appear to have now would be fine, if genesis (which i doubt you are) then you would likely use ball-like objects as leg segments to save space in the graphics, although if you were working with later snes games (yoshi's island, etc.) or gba game limitations, you'd be able to rotate and skew the leg segments and such to make it more smooth (such as certain things in the sonic advance series)
personally, i think the walking animation would work best with 8 to 16 frames as it is a fairly large object with a larger 'circle' the feet move in
if you are working by general snes limitations, the current animation you appear to have now would be fine, if genesis (which i doubt you are) then you would likely use ball-like objects as leg segments to save space in the graphics, although if you were working with later snes games (yoshi's island, etc.) or gba game limitations, you'd be able to rotate and skew the leg segments and such to make it more smooth (such as certain things in the sonic advance series)
personally, i think the walking animation would work best with 8 to 16 frames as it is a fairly large object with a larger 'circle' the feet move in