A combination of a zbrush practice sculpt and some photoshop doodling.
The second image is a Poster variation created for various products on my Zazzle store.

If you like these designs please share them on your social media networks, it will help me greatly in getting these products out there.
Cheers!

https://www.zazzle.co.uk/dark_atomic
https://www.zazzle.co.uk/dark_atomic/trigash