Here is a collection of all my Castle Grayskull pieces which I've made over the last few years. They're quite popular with the fans of the original Masters of the Universe cartoons (Which I loved as a child). I also sell prints of these in my Etsy store: 

www.etsy.com/uk/shop/nostalgiapunk

sketch process for the above. I ended up using the foreground of the last thumb and then showing Grayskull face-on.

This version has gone viral on Istagram, Imgur, Twitter and has been one of my most popular pieces of all time. It was the first one I made and I've never been able to make one this popular since!

These next pieces were designed to be more realistic. Like a movie set design.

Here's the design process. In the end I just kept it simple, like the original design.