Cool stuff! Something I noticed, if this is an isometric character, shouldn't the little boys left leg be shorter? This might not work well with this particular design though.
Since you have 6 frames, I think you should push animation further to make things more interesting. I really like the little boy and how reacts to the robots movement. The robot could use some more movement within your animation maybe. I don't mean more frames but using your frames differently. Here's a small edit I did. Disregard that shaking on the leg though, I was experimenting but it's not looking that good. Your animation is slow too. I changed the pace a bit too.
Also, why are you working at a 320 x320 canvas? That's a seriously big canvas for something that can be equally.accomplished at a smaller scale. I'm not sure that's what you should be doing. Reduced that thing to 64x64. I think that'll give you a canvas big enough to recreate this with the same detail. Here's I'll reduce it for you. Just recently discovered photoshop will change pixel art images for you without distorting or very little pixel distortion!! Maybe you don't have photoshop and remaking this would take time.
edit: not saying my animation is amazing or anything. just saying you should utilize all 6 frames you have in a more dynamic way.
