Carl, have confidence in yourself and the pixels. You are in no way operating in the smoothest and most efficient way possible, so saying that you've achieved some kind of ultimate limit sounds silly - if your reply to critique is 'I've exhausted the limits of the current format' then it's the same as saying that your image is ultimate and impossible to improve.
I don't think that's what you wanted to say, so man up and believe in the pixel * U *
I think you could've worked more with posing in the process of making a mini-pixel jehuty, never mind if you get the basic shapes down if they're in a placement that doesn't convey jehuty's silhouette and posture - the bend of the spine, etc, are things that are very significant in Jehuty's build. This one leans forward - the original jehuty always had that hips thrust forwards thing going on.
Working larger seems like a good idea, though, cause you should aim to feel completely safe with the pixels and their quirks when you try to create recognizable form in the small space that this format provides. But it is indeed possible to take this further and make it better gloriouser : DD
I feel sad that I can only explain my points with edits right now, because it's hard to offer good emphasis on what you really want the receiver to take to heart. Oh well! Good luck.