If I were to, say, brew mead, and say, eh, borrow the label from the in-game Black-Briar meadery for my homebrew mead, what sorts of legal issues might I run into, if any?

Are you selling it for profit?

If it were kept to you and your friends, and no profit was being made, I doubt anyone would care. But the second you sell it, you'll have Bethesda up your ass the second they hear about it.

It's best to PM Gstaff or http://www.gamesas.com/eng/contact_email.php if you have a legal question like this.

If it's not something you are selling, and you don't make too many, chances are they'd be happy to see photos of it posted in the Elder Scrolls fan art section - at that point they'd probably consider it a replica. Of course if you do sell it with this label, or if you produce a large number, I doubt they'd be OK with that.