I don't think I've ever heard anyone tell someone they were pixelling too small before.
I made an edit for you.
You constrained yourself to an isometric box. This isn't always good. It's best to be dynamic! because things end up looking lifeless and boring when they're following a grid of some sort. In addition to following the contour of the reference more accurately, I made the highlight stronger. I noticed you're using a lot of diagonals for the interior highlights. It's tempting because 45 degree angles always look nice and clean, but it isn't all that accurate to the reference and can look weird because that's not how light should go. Your palette seemed pretty static, it tended to stay near zero in terms of hue, but it works pretty nice and I made only small changes. :3 Pay attention to useless colors, it's extra work for you and muddies up the piece.
I didn't carry out my critique/edit as best as I think I could've if I had more time, but I think I covered everything well enough for you to be on your merry way pixelling! Just work closely to your reference, notice subtleties (such as the foremost and backmost verticies, in the picture they're offset!) and you will be fine.
I just previewed my post and you've replied, awesome pixel work for a coder! I don't think 64x64 would be easier, at least in my opinion and experience.