Traits

Smooth horns with little to no texture and stick straight in a single direction.

Horns that have small protrusions or ridges on them as a sort of texture.

Horns that curl behind the ears to the front near the cheeks. 

Horns that curve in only a few ways, but are generally smooth in texture.

Only Lupini of uncommon or higher rarity can have horns.

At least two of the 6 horns hook under the ears back towards the face.

Horns are bone or keratin extrusions from in and around the head. There is no rarity to choose for bone or keratin, nor do they affect formation, type or length.

Bone horns are generally very natural colors ranging from white, black, gray, cream and brown. Once broken they do not reform. A body modification trend with bone horns is to carve intricate details into them, and sometimes those carvings are filled with metal.
Keratin horns are far more unique in coloration, ranging from metallic (looking, not real metal) to resinlike, so on and so forth. They can shed off and regrow, but any modifications (such as metal melting) will be shed with it.