I was all set to prime and paint the inside. I do like the warm color of wood - always have. Once I got a bunch of OSB on the walls and started covering most of it with shelving, cabinets, tool boxes, peg board, etc - I decided to just leave it. It would be nicer if the OSB didn't have the ink printing on it, but there is so little of it exposed that it's not a big deal. The wood will age over time and it seems to lend a old school effect to the walls. I've been fortunate to have some kind of shop since I was about 10 - really - and none have had any kind of inside finish. Father and grandfather shops were the same, so I may just be pre-disposed to the look. That said - if the walls were sheetrock, it's be white.