There are tons of ways to mount your boards in the garage. I will be working on a rack myself sometime in the future (maybe not until summer though). Here are a few links to different types people have posted before that I was looking at.
Some one made a suggestion that when you put them in the garage, put them at the height of the boat (so you can put them in and out of the boat easy, instead of putting them lower to the floor).
I like the ones that HITMAN has at the bottom of this post: http://www.wakeworld.com/MB/Discus/messages/65921/45703.html
Here are some others, that seem they would be more out of the box: http://www.wakeworld.com/MB/Discus/messages/65921/462775.html