Long time reader and browser of the forums. Bought our first house about a year ago. We decided the bonus room above the garage was perfect for the game room.
Took me about 3 months to finish the bonus room as it was a hideous mess of what I call "pinterest gone wrong"! The room was ALL BROWN. The parallel walls were all thickly stuccoed and painted brown then washed over with a darker brown. The slanted walls were also brown, just a slightly different shade. The ceiling has wood paneling. Which was nicely nailed, screwed and glued to the ceiling that was bare dry wall...that took a long time to properly fix. Not to mention wood flooring (which I kept).
The parallel walls had to be sanded, took me 2 weeks to get it to a decent thickness and attractive texture. Really just cursed the entire time that someone had thought it looked good. Wish I could find the picture. Then it was fixing the ceiling. Which wasn't too bad but I still remember the shoulder pain from having my arms up for so long. Last bit was just painting. All of this I did myself as my wife was pregnant at the time.
I created an album on imgur of my game room. I am pretty happy with the results.
http://imgur.com/a/0Hukw