There's the Old Mars skin from the deluxe edition, but it seems that's just for the miner set and the cutter

I had one option for a backpack skin available from the deluxe version (don't judge), but that was all so far. I haven't finished any major quest lines though,

I was able to apply a Constellation skin to an equinox, apart from that I've not noticed anything else I could apply a skin to

I found a skin last night on some pirate but I didnt actually check what it did or what it really was

I'm hoping modders use that tab for their new textures. I see a ton of remade guns but I'm holding off until the modding tool comes out so they can be made into skins instead.