/ic/ - Artwork/Critique

Two question, seeing your thread I poked my head around RB for the first time. A LOT of peoples merch are things like doodles of Starbucks cups, Hot cheeto bags etc with the logos being recognizable. What the fuck is the legality behind this? Some of the best selling stuff on the site is literally fan art of "Brand name" items. Can you really get away with that?

Secondly, a lot of art there I see resized up and down to be put on not only shirts, but small items like mugs and phone cases. How does the website handle that? What resolution would I need to make something in to confidently know it wont look like ass if someone orders something big or small?