Rules for prints are simple:
Only sell original art that is yours.
If you are producing work for a studio or clients, you need to be clear about what rights you retain and whether you have a license to sell the work as prints.
Fan art is very tricky. Because of the risks involved with fan art, we have a blanket rule that no fan art should be sold as prints on ArtStation.
The issue with fan art is that it risks infringing on intellectual property copyright & trademarks. The reason why companies/studios care more about prints (that can be mass produced/manufactured) vs fan art on your portfolio or the odd commission/print sold at a convention, is that it competes unfairly with their licensing business. Many entertainment companies sell licenses to manufacturers to create products with artwork from games, movies and known IP's. Companies pay a lot of money to license the rights to manufacture products based on famous IP's. If you do not have a license from the IP holder, you cannot make your fan art for sale as a printed product. You can get sued for that.
Let's put it another way. Suppose you created your own original IP. Some fan comes along and creates "fan art" and puts it up for sale, which competes with your business. You'd be pissed right? It's the same thing.
Your work should definitely not contain any official logos from games/movies if you do not have the license to do so.
So yeah. No fan art for sale as prints.
If you see fan art for sale on ArtStation Prints, please report it either using the Report Abuse link on the product, or contact us at email@example.com.
Note: Fan art is allowed on the non-commercial parts of ArtStation. E.g. you can host it on your portfolio. Companies generally won't go after artists for creating fan art, and unless you're trying to pass it off as official work, they're usually cool about it (although, they do reserve the right to enforce their copyright). However, they will go after you if you are selling fan art as print/manufactured goods without a license.
Same rules as on the community gallery. Read it here.