I saw that a Psi-controlled Chtyssalid had a "stun rod" image as a melee image, so I started drawing melee sprites for aliens.
I looked at the in-game ufopedia for reference, but I drew it from scratch (not a copy/transform of the original art). I release it to public domain - feel free to use or modify.
Still have zombie and reaper to, from what I can see of the rul files (entries that use "bigSprite: 26")