I think 4 arms would be a nice start!

+1

First, maybe is a cliche, but it is a good one
Give him a new head, sharing his body with someone else, so both of them can have some fun with more changes c;

+1

Just let him grow a second head xD That is going to be uncomfortably close and will squish his cheek with his new mate >:O

something snake-like

Something taur. Taur tfs are always fun

Turn em into their (or your) fave species! Or maybe conjoined to said species… ;)

A snake for a tail!

Seconded!

dragon bois are cute

Gender swap!

Seconded

How about an insect abdomen?

Extra nipples!

give that man a beak

You gotta have at LEAST four arms.

And a second head makes sense, given your other work.

I'm going to agree that something snakey needs to happen. A snake for a tail was suggested already, so I'm going to second that. But, if he ends up with a snake-tail and two heads, then maybe this should be a chimera TF? One head lion, one head goat, and snake tail.

If he/they end up with four arms, as well, two of the arms might be lion-style and two might be goat-style.. unless of course you choose to go with goat lower body and lion upper body or vice-versa.

Allow me to suggest a new idea: a forked snake's tongue for him, in general. If he ends up with two heads, it could be a feature that one or both of them have.

If he becomes a chimera, it would be all the more 'monstrous' to have a lion and a goat with forked tongues.

Sorry if I've provided too many ideas! At least most of it could work together for the chimera idea. >___>