Interior wall material in your shop?

hmmmm, texas eh! guess you probably don't need heat or insulation but drywall painted white would be nice ,, I guess ,, maybe,,,

 

osb and painted it grey works real well

 

It makes no difference to me what you do.
But you asked because you're worried about fires.
I told you my first hand experience, 1/2 drywall ( unless type x) burns, OSB burns painted or not, same for plywood unless its fire resistant, paneling and peg board burns, fiberglass (Frp) burns actually the resin ,

5/8" drywall doesn't burn with a few exceptions - not type x or there's a blistering inferno for over an hour. Now this is a bit tougher than regular old 1/2". There's extra thick paper and fiberglas reinforcements in the board. It tolerates more abuse and not as easy to dent as regular old drywall.

Looks like you're back to steel siding

 

Mine is a standard stud wall insulated with 1/2" sheetrock but I have extinguishers on all walls just in case. I also don't weld or make sparks right before closing up. Sit down have a beer and make sure everything is cool...............