Diamond plate bright aluninum.
He said he was on a budget...but that would be uber cool...
I would for sure 'look around' to find a closeout deal on tile. i did that in 1991 for the very first garage i had (new house).
i got the tile for $0.25 each for 12x12, plus the adhesive & the grout. in total i spent like $40 bucks for the tile, maybe $100 bucks with the adhesive & grout.
you gotta make sure the wall is super clean before you start the job. i ended up having to sell the house a year later, drove by last summer, tiles still there & looking good.
i regularly see 'closeout' tile around my neck of the woods these days for $0.75 each (12" x 12").