I hope this isn't considered off topic... My shop is used for what most of yours would be... mostly wrenching but a fair share of cutting, welding and grinding. My shop is simply wooden studs and sheet metal exterior. The interior looks just like you imagine. I've alwaus been afraid of that ONE spark or spec of slag that makes a new home in one of the millions of hiding spots between the exposed studs and sheet metal. Although metal roof paneling would be the obvious safest and easiest material to line my walls, what would be a more visually pleasing material? What do you have?