What do you want to put in there? Vehicles, other stuff or all of the above?

Well I assume both vehicle and storage...

You could put adjustable shelves across the back. On one side - near the back - you could install a 'tool bar' that holds shovels, rakes, etc - vertical by their handles.

This Old House, or maybe it was the Ask This Old House segment, recently had a makeover of a similar garage. The owner wanted to use it as a workshop part of the year, but needed to store a car in certain months. Tommy gave her a nice setup with shelves, pegboard, and a fold-down work surface with storage above. Maybe it's available on Youtube?

you can have tool cabinets hanging at the back. A small washing area at the corner would be good also. Try to paint it with grey.

White paint on the walls, new brighter lighting, and new painted floor will fix it right up. This link shows some great before and after photos of a similar garage. http://spotofteadesigns.com/garage-makeover-part-i/