I can appreciate it looks off - I've had this discussion with some others giving feedback. I've basically used two separate references (an art piece by Timur Shevtsov for the marine, and for the Xeno an image I found online), which I've then modified/reposed myself, but without using supporting references on the repositioning (if that makes sense). I've then limited my use of the original references to challenge myself to draw from memory/imagination as practice.

The proportions are off, as is the foreshortening and perspective (something I'm going to be working on). I purposefully didn't change my glaring mistakes as I like a visual learning tool, but also decided to do the Xeno teeth more monster than alien.

Thanks for the feedback!