One of my players is very excited that he got access to the find steed spell. He wants to make it way cooler than it is written, by way of flying creature or (specifically) an aboleth. He recognizes that’s dumb over powered but he is just so excited to have a mount. 

I want to do something cool for it without making it unbalanced. I know we can mechanically keep it the same, and just reskin it to be whatever we want it to look like. 

I was wondering if anyone had any other ideas on how to make find steed any more exciting. Thanks. 

I gave one of my players a Giant Lizard as their mount. I let them choose between the Hold Breath or Spider Climb ability, they took Spider Climb. It made for a fun unique mount.

I think I may just have to burst his bubble. 

I think I'm going to make him choose what steed to pick when he stocks Summon Steed. 

Or maybe her can pick one steed that will always be summoned when he summons a steed. 

He can use it to spider climb, but that's it. No flying. 

I would say that he could replace it with pretty much any CR 1/4 or less beast, without a fly speed.

Eventually he can get to Find Greater Steed, which lets you get certain CR 2 beasts, I would probably allow a beast with a fly speed at that point, since its level 13+

There really isn't a balanced way to get an aboleth as a mount.