Lots of outlets along the wall @ 54"-60" off the floor. Put them @ 48" and 4' tall stuff still covers them. Put multiple outlets in the ceiling as well and get some drop-down reel extension cords, it's nice not to have to trip on cords.
If you're using a design program from Lowes, Home Depot, Menards, etc. Double the amount of lighting, shadows suck balls. It's way cheaper to double the lighting up front when you can pull wire sans sheet-rock. Not needing trouble/work lights for most projects is worth the cost of the extra lighting.
Figure on adding ceiling fans. Whatever it takes to eliminate "cold spots". Ceiling fans really help dry the floor as well if you spill something, bring in a snow covered vehicle, or just need to dry/de-frost a snow-laden/wet ice house.
10' sidewalls at a minimum if you're going to hang anything bigger than deer heads and want them up high enough to be out of the way of most projects.