It's generally pretty good - I played around with it and I have just a few things that could make it better.
The bottom of the robe is kinda pointed..get rid of those bottom 2 pixels to fix this.
Generally, in MC the bottoms of sprites have black outlines - this sprite completely lacks it. So I would go and put some black outlining to the bottom of the robe.
The colors on the robe need more contrast - the lightest shade in the robe is hardly different from the next lightest shade so it gives it kind of a plain look. So experiment with colors a bit.
Lastly, he has no face...?
I hope that helps. Again, good job!