The First Amendment provides strong protection against government attempts to censor violent art, so the chances that you’ll run into legal trouble are low. But there are still some things you should be aware of, and this section includes some practical tips on how to avoid legal trouble, as well as some pointers on how to make the way you display your violent art more user-friendly if you’re concerned about fielding complaints from people who don’t like your art.
The government can’t forbid violent content, and can only control it in very limited ways. In general, if your art is just graphically violent with no sexual content, you're not likely to face legal challenges to your work.
That said, if you want to avoid conflict over potentially controversial work, you might consider putting particularly graphic material behind a warning to users that some viewers might find your work disturbing. This is a relatively simple way to avoid complaints, either directed to you as the artist or to the service provider hosting your material, since those viewers who might be offended by your work can choose not to click through.
Obscenity is generally illegal under both federal and state law. The government can prosecute you for posting obscene violent material, though it takes a judge and jury to decide if your art is obscene. There must be some sexual component to a work for it to be considered obscene.
Read the terms of service before you post so that you know what is and is not allowed (if they’re paying attention or receive complaints).
The threat, however, has to be fairly specific, directed at a certain person or group of people, and likely to happen soon.