.gifs are fine. Everybody loves .gifs. Images, too.
But if you're going to post a .gif or image in the comments that contains sex/obvious sexual things/porn/epic violence/gore etc etc, please just link it instead of embedding. Some nudity is all right as long as it's not sexual -- you know what I mean, just think twice.
As a note: this is NOT the same thing as triggers and I'm NOT requiring anybody to warn for anything (though that'd be nice of you). Just following the basic TOS of the site and making sure this comm is NOT 18+ only -- the same reason things like epic guro and porn in actual secrets are only linked.