Great idea....I have seen couple of hundred pics of showcase garages in some recent books and in many posts on Ferrari chat and Corvette Forum, among others.
Many people end up throwing up some neon, tool chests, shelves, and a rug/budget couch/stools that dont seem well planned/used.
The main test is would you enjoy spending hours there AND could you host a 'car night' for buddies/gals who would want to stay v. escape gear, musty fumes.
Some folks do a barn/lodge theme; others a NASCAR pit, a vintage collector showcase or VIP Winners Circle Club
I would focus on combining at most 3-4 areas in the space with focus on a theme, utility, and enjoyment
-Car area
-Memorabilia/Gallery Area
-Social/Bar Area
I have been working on mine for 3 summers and have converted a 20x20 (its NY) basement / laundry room / 1 car garage (budget under $5000)...its pretty unique..its not even done & I have to kick visitors out.
-Strcuture: drywall, insulate and make sure you connect heat, a/c, plenty electrical
-Car Flooring: "U-coat" it, or a race deck, or tile: checkerboard or cobble-stone style
-Social-area: flooring Engineered wood floor over underlayment over sub-floor (see cozy)
-Storage: locker or chest for tools, covers, chargers, oil/fluid, wax/towels, parts, booze, ammo....lots of clearance from car!
>Car Area
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I went with a Le Mans 'Pit Stop' theme: hung 20+ flags/banners of Manufacturers / Sponsors / Race circuits that GT raced on from Goodyear, to Gulf, to Sebring. They are all 3'x5' an can be bought for $20 online/eaby. Other ideas are actual metal signs, neon and lighted signs which are nice but pricey.
>Memorabilia / Gallery
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-Recessed lighting
-I ordered some large (3'x5') framed vintage Formula 1 / LeMans posters and hung them along 1 wall to create a racing gallery. Giclee repros are nice and about $175/ea. On other walls I got 12 large wood frames w. matt. from Pottery Barn and framed photos of every car I have owned and vintage family rides. I laser printed some B&W/Color GT pics as well. Used all same sized black frames and when lined up it looks like a photography collection. Frames were $20/ea., pics free.
-My Brother created a built-in oak wall unit with nautical style cabinets w/ inlaid flush brass hardware, shelves, desk and 42'' TV stand pre-wired w. dvd/cables/speakers. Shelves: GT models from 1:72 scale to 1:8; Heuer F1 clock helmet collection; trophies/plaques, old Bell Star Helmets in Yellow & Orange, small library of car books.
>Social Area: Bar w/wine cellar theme
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-Laid wood floor, with 3 piece side trim.
-Built Oak Bar Cabinet w/doors w. black granite top remnant; other piece to desk.
-Panelled Bar surround with Wine crate panels: all Grand Cru bordeaux or cool crests.
-SS Bar fridge under cabinet; $150.
-Black & Steel Le Corbusier LC2 Cube Club Chairs...colors/style same as GT interior. Very tight, can be arranged arround for drinks or lined up for movies or race day.
-Cigar humidor chest, ice bucket, shaker, etc.
-Poker table/chairs
I basically created a home depot/mini-version of those million $ garages in the books. They all had the same 3-4 themes: the visual history of the marques; tools for utility, preservation, use of the car, and areas to enjoy motoring friends and lifestyle.
The test is I just enjoy stepping out of the GT, pouring an ice cold Heineken and listening to the GT exhaust crackle while it cools down, and heat wafts in a few feet away....priceless.