I'm just wondering if Bethesda has copyrights on Nuka-Cola and the Vault Boy character, or has registered them as trademarks? In what ways am I allowed to use them? I understand that I can't use them for commercial purposes, but how about e.g. printing a single t-shirt at Custom Ink (or a similar company), for personal use only?

You could, but you need to make sure licensing claims and copyright is taken care of, like when youtubers put song on youtube.

Just for yourself or will you make for friends and such? If its just one I think your good, not really a vault-police watching your every move. :shifty:

No, it's just for myself. But I do need to upload an image to the company's website where I design the t-shirt.

I'm pretty sure you're fine as long as you don't sell it.