I assume you mean yaoi and yuri, or yaoi and yiff.

If it is sexually explicit in any way, no matter if it's homosexual or heterosexual, you'll be in deep crap. If it isnt sexually explicit, it's fine. Simple. You wont get banned for posting a picture of two girls kissing, as long as it isnt explicit.

For future reference - yaoi and yuri refer to explicit homosexual stuff. Shonen-ai and Shoujo-ai refers to the more platonic sort.