There isn’t much to it, really.
1. Drive to Wal-mart and buy “dent-free” drip pan (found in the automotive section).
2. Drill holes in the pan.
3. Attach to the wall.
4. Add magnets.
You could also paint it with blackboard chalk paint or section it off with colored tape. Lot’s of other ideas on Pinterest.com just search “oil pan” and see what you can create.