Floor:
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I used U-Coat-it, its commercial grade; they have a $400 DIY kit, and it came out perfect. After 4 yrs no problem. Hint: Do the Polyu top coat; it has a hyrgroscopic/psi rating that prevents moisture, vapors, seepage. Lenos uses it.
http://ucoatit.com/pgs/main.htm
Leno Ads/ Petroliana / Signs / Neon
I researched this and found that there is a whole collecting world associated with this area alone. One can spend $25,000 easy.
The majority of Leno's stuff is vintage Grand Prix / F-1 posters; with some euro-marque showrrom advertising. Some appear original; while others are blow-ups.
The best bet is to get a good quality on-line frame shop that has these photos digitally and can produce giclee prints in 44x60 wooden/matted frames. You can also do massive vintage movie posters like: Le Mans, Grand Prix, Winning and some euro ones that are 7 feet tall. Or, black/white racing shots.
I have used below, with good results
http://www.allposters.com/-st/Auto-Racing-Posters_c7485_.htm
I have also done the Pit-Banner/ Flag route. These are silk/poly flags that are form 3x5 to 6x12 that look amazing in a garage. You can get them for race-tracks: IRL, Indy, Sebring, Daytona; or you see these in F-1/LeMans pits and are a range of sponsors from Martini, GULF, to Rolex, Michelin Man, AGIP Romulus Wolf, Dunlop, Camel, etc. They go for $25-100 and in my opinion add the most punch/$.
Lastly, you can go with neon, back lighted signs, etc.; some sell on ebay, others are custom.
Bar/trophy case
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I would add an area/in off the garage where you can put up some shelves/case for GT models, plaques/trophies, helmets; or have a cabinet with a steel mini-fridge, dead-sink, and counter.
It helps to store car cover, rags/buckets, tools, GT parts deep-storage or better yet a mini-bar.
I did a small cabinet with a $150 GE SS under-counter fridge, black granite remnant slab $300 and wine-box panelling $150, 2 directors chairs. Its nice to have cold beers, ice/mixers, chips after a drive or when visitors linger as you give them the GT story.
MISC:
Unless, you have a/c look into dehumidfiers, heat register, an alarm or even better a dog!