Mine is 24'X22' sheet rocked and painted. I put in outlets 4' above the floor and spaced every 6' along the two side walls (all GFI or conected to GFI). I also installed lights in the ceiling. I put down black and white vinyl tile on the floor to give it a cool look. I have an 8' rolling metal bench on one side. There are upper cabinets along the walls. (I got these for free from a friend redoing his kitchen.)
But my kids are teens now so I gave up my garage so they could hangout there with their friends. In a few years I will get my garage back.
(In pic three you can see the steering column I cut down for my truck.)