I finally finished the inside of my 25 year old garage last year. I used varnished pine car siding on the ceiling. On the walls I used exterior, primed grained/grooved Smart siding 4 x 8 panels. The only one wall I had drywall on, I removed and put up siding. Looks great, waterproof, and tough. Plus not joints to finish!!! Painted it a light satin grey for color. White shows the slightest amount of dirt. I found the light satin grey a good compromise to show less dirt, and keep it bright. The backside of the doors are off white for a little contrast. And you can't have too many lights any color.