Not much to say, it's your canvas. Sounds like you got the big stuff figured out (air, power, exhaust).
Insulate it 2x more than you think you need if you live in a climate where it can get below 0. You'll never regret spending a few extra bucks on insulation.
When I built my shop space, I went OVERBOARD with power outlets, dedicated 20a legs for each machine I run, lights on their own circuits, outlets on the walls every 4 feet, duplex outlets for everything. Nothing is more annoying than having a few things sucking power and tripping a breaker or having the lights flicker. I've already found something to use each outlet with. Can't have enough outlets.
Everything else is creature comfort. I threw a smart TV in my shop so I can watch accu-stats in the back ground while roughing out tapers n such. I got a bluetooth radio for listenin to podcasts or tunes when doing work that requires my visual attention. I added some nice shelves that double as light duty tables for assembling parts / cues. Mini fridge so I don't have to walk my ass upstairs for a soda.
What else.... Vintage signs, ads, ephemera from local machine shops is a must, oh, and pin-up gal photos. Then you're set.