I (Luchu) am pretty relaxed when it comes to what you can do with your rixgem. But there are still restrictions.
You can:
Draw them in NSFW as long as it's legal.
Commission others to draw your rixgem, and get avatars of them.
Have them be any sexuality/romantic/gender. Most places on their planet are very accepting.
Make them have physical or mental disabilities as I think it's stupid to not allow that. The only rule is if they are deaf, their gem sensor has to be very small or in the case of acquired deafness have the sensor be shattered.
Hybridize them with other species. Though if you do so, they must lean heavily one way or the other. You must have permission from both me and the other species owner.
If you are wondering, yes I'll allow you to make a rixgem a myconian no need to ask me. Just know that if they become a myconian their gem parts are replaced with mushroom stuff, and (this is just for flavor) that there is a slight chance that the mushroom sensor won't work correctly. (i.e: deaf and/or not being able to smell)
WHAT YOU CAN'T DO:
Draw noncon NSFW, cub/baby fur NSFW, or anything like that.
Draw them in hateful content. Rixgems are made for everyone no matter sexuality, gender, race, or nationality.
Hybridize them with fandom species that don't allow you to do so. You can't make a Rixgem-Dutchie for example.
I have zero tolerance for (no)maps and/or zoophiles. I refuse to let others be traumatized and injured.