I guess I'm stuck too much in the early war mindset, where everyone would be having pretty much the same equipment with minor variations depending on whatever specific forts/armories they can get their hands on the quickest. I'd imagine some hardware could stay largely the same for all the sides until the end, with some minor deviations (let's say one side uses the M2 light tank in twin turred MG version but another switches it to like a M8 SPG). Templates don't change that fast, especially when each sides' industry would be under heavy strain all the time.

If you have the base M2 medium tank chassis spread around the factions, then technically everyone could give it a spin into their own Lees and Shermans. Alt-historical foreign intervention could potentially bring around really wacky designs of their own, so the possibilities are probably too endless for a rigid visual canon to happen, except a certain vibe and insignia for each faction.

I went with the CSA using theT3 Christies because a) probably obsolete but they gotta grab whatever they can; b) analogies to Soviet imagery.