This is pretty cool. I like the little details, and the way the knees move/are attached in the run cycle. The horn in the back of the neck is odd, it's intersecting with the back while it moves in the run cycle, i.e. it should have some kind of 'hole' or gap or something to move in. The tail is very stiff, i would suggest breaking it into 3-5 segments or something to make it flow a bit, because atm it looks like a stick pointing out of his behind
One last remark. When I look at the run cycle from behind, it looks like he's running in high heels xD. You might want to change that, then again if you're happy with the design it's your choice. I'm just critiquing in an effort to help
If i offended you in any way then I apologize.
So far, great job, keep it up.