I'm in the process of completing the 'shed' to house my growing Panzer collection. Click on the pictures to enlarge them.
It's a 34' x 28' building (including the lean-to) that I spent over 2 years designing. It's a compromise size - I didn't want to finance a bigger building with the economy the way it was.
My neighbor did an outstanding job of the site prep and pad, then a friend of mine put up the outer shell.
My dad and I put siding on it after my father-in-law directed my wife and I at putting the garage door in.
It's been quite a project.

You'll see when you browse the pictures that a lot of thought went in to putting enough space for tractors to fit in. I've decided to embrace flat surfaces - the ones that tend to get cluttered with junk. There's a 10' x 16' platform inside with a 4' x 16' extension along the wall. The platform is 4' from the ceiling, giving me about 6 feet of head space to walk around.

Some hints for your own 'shed':

• Build the walls with 10' 2x4's - not studs. This gives 10' 6" of wall space (including top and bottom plates, plus any elevation above the floor from the concrete block base.
• The 16' wide door makes the 24' wide building look symmetric.
• I used a 9' tall door both to fit my F250 Super Duty inside and to make the building look smaller than it is.
• It will never be big enough - get over it.
• Insulate the walls - even if you don't plan to have a heater.  It deadens the noise.
• Epoxy the floor before you move anything in.  Don't use cheap epoxy like Rustoleum - get good stuff.  I use Pratt&Lambert 2 part industrial epoxy in a light gray color. 
• Use 'attic' trusses.  This gave me a 12' wide by 6' tall (at the center) x 28' work shop above the main floor.
• Build the stair case to code.  I had to re-configure mine so the building inspector would approve it. 
• Sky lights and a gable vent fan are necessary in the attic.
• Put 7/16" OSB or plywood on the walls so you can screw shelving in without trying to find a stud.
• Paint the walls white - even if it's white primer.  It'll help illuminate the whole garage.