I love XCom and the Sectoids (the game's “grey” aliens), and I wanted to try my hand at redesigning that alien species.
I used triangular forms to accentuate the creature's danger & malice, while also trying to keep it thin & feeble (as Sectoids are basically grunts). Visible implants helped add a little storytelling and suggest how the Sectoids have been "engineered" to fight.
The textures pulled from the original designs and the wet, translucent skin of amphibians (emphasizing the creature's fragile & "alien" qualities; plus, the Sectoid’s implants probably generate lots of heat = sweat). Ultimately, I used 4 texture sets and the Substance Suite to push the details as far as I could.
Final Polycount: 10,390 Triangles
Texture sets: 4 (head, arms, torso, weapon)
*3D Coat: Retopology and UV layout
*Substance Painter: Texture painting
*Marmoset Toolbag: Texture baking and Rendering
*Photoshop: Final compositing