I'm in your boat - 20 x 20 attached garage with 2 cars in it in the winter, one in the summer. I've stared at my tiny garage so many times and dreamed of what I wish I had, when what I should have been doing is looking at the space I do have and maximizing it. I've finally got started on ti and I've been getting ideas from these forums.
1. Decide what the space is for and limit it to that. For us I put every yard-related tool (hand, electric, gas), equipment (wheel barrow mower), and supply (fertilizer, sprays, and related equipment) in a shed in the back.
2. The garage is not for house items. Wife has the kitchen, closets, cabinets, basement, etc., that I don't intrude on and she's accepted that the garage is my one space I get to decide on.
3. One wall up against my wife's car is never going to have anything on it like pegboard and things hanging on it, etc. - I'll give her that "clean" walkway. So I have to scratch it off the list as useable space.......except for maybe fold-up workbench?.....that thought just struck me.
4. Finally, get it off the floor. Old cabinets, shelving from COSTCO, whatever. I put my compressor hose reel high on the wall between the rails of my 2 garage doors, which is space with limited usefulness, except for that skinny reel. And the air pipes will run above the garage door on a wall that again will likely never be used for any other purpose.
Good luck and add pictures when you're done.