Some pretty loose guidelines are as follows:

Nothing sexist, racist, ableist, homophobic, transphobic, etc. I’m not going to say nothing violent, because this is a comic book tumblr. But there is a difference between She-Hulk punching someone in the face and torture porn, so let’s try to stick to the former.

Basically a good rule of thumb is ask yourself “Is this ok to submit?” If the answer is “No,” “Maybe,” or “I don’t know,” then it probably isn’t.