Well, most houses that old didn't have garages when they were new...

They may have had a stables or carriage houses that got converted, or nothing at all, but I don't think garages became very common until the 1930s or so. I live in an older neighborhood myself (my house was built in 1913, most houses around here date from 1905-1915.) The bigger houses have carriage houses, while most of the rest have garages that were built in the 1930s or 1940s. The interiors of the carriage houses tended to have beadboard on the walls and ceilings, and maybe a simple workbench in the corner but that was about it. The carriage houses at the really big mansions do have upstairs apartments where the chauffeur lived, but they generally were finished simply...the rich people back then didn't waste a lot of money on the hired help.

The garages were pretty much unfinished, just bare studs.
I did replace the 1940s era single car garage in my back yard with a new one that's 24x40. The exterior is sided and trimmed to match the house, but the interior is still unfinished. One of these years when I finally get around to it I'd like to use beadboard, or more likely 4x8 sheets of plywood milled to resemble beadboard, but I'll probably paint it white. My neighbor's old garage still has the original beadboard walls and ceilings, and while it looks very nice the wood is so dark from age it's kind of like a black hole in there when trying to work on a car.
You may want to look at pictures of kitchens from that time period to get ideas for wall treatments and cabinets/countertops - I think a lot of the style components would work well and it would fit the time period.
I posted these pictures here a long time ago, but I'll post them again. These are plans for a carriage house from one of my dad's college architectural drafting textbooks; if I remember correctly the book has a copyright date of 1927.