So I accidentally bought a chest texture I don't need, what do I do?
Refund maybe, please?

You cant do that. The only thing left to do is:
1) Use it.
2)PM the seller and try getting a refund.
3)Try selling it on the forums.

I bought only the slot for a texture, not the actual texture.

Then your screwd man,
Dont know what to say 3:
But you could Buy the Actual texture then sell it
But if you don't have teh moneyz

Then your screwd, Sorry to say man.

Guys. He bought the item. Not the art.

You can't have a refund, you have just wasted 2k on a texture :3