Shelves, Cabinets, some pins (or holes for pins) for securing Car Ramps [for when you want to work under your car for misc.], and a sink.
An oil-filled heater would be suffice for heating a garage, they're the most efficient for the purpose you're trying to achieve.
I'll take a pic of my garage to give you an example, but it doesn't have to be as fancy. I spent ~$2,500 (including tools) on my garage while doing it myself... took me about 2 months from measuring, buying tools, cutting, and securing all the wood, handles, and everything else. Good stuff...
WTB: 3 Stage Intake Manifold and components - PM me your asking price.