Lv. 1 - Lv. 2 horns use unique texture layouts to account for asymmetry, while Lv. 3 - Lv. 5 horns share the same texture for both horns. This means that apart from the first two levels, it is not possible to texture each horn separately.
The full horns use basic basic and intuitive mapping, where the bottom of the texture is the root, the top of the texture is the tip, and left / right matches what you see when facing the head.
Lv. 2 horns use the bottom half of the texture for the right horn, in the same was as full horns do, while the left broken horn starts at the top half and progresses downwards. The end cap of the broken horn is mapped separately to avoid distortions, and is located in between the other two elements.
Lv. 1 horns position the left horn at the top, the right horn at the bottom, and place the end caps in the middle, where the left half maps to the left horn, and the right half maps to the right horn.
Note: I chose to inflate the bottom middle area to give more texture density to the harsh curve, which wasn't necessary on the other textures. This means that straight horizontal lines should follow the horn growth patterns of the default textures, while vertical lines are unaffected. I apologise for the inconvenience this may cause.
While the maximum custom texture resolution caps out at 256x512, I recommend using the defaults: 128x128 (Lv. 1), 128x256 (Lv. 2), 128x128 (Lv. 3), 128x256 (Lv. 4), 256x512 (Lv. 5).
Variant Colour: Demon (#333333)
Variant Description: The default textures.
Download Link: Sins of the Past (Lv1 - Lv5).zip
Variant Colour: Ivory (#EEDFCC)
Variant Description: A more natural look.
Download Link: Gnawing Marrow (Lv1 - Lv 5).zip
Variant Colours: Demon (#333333), Mysterio (#CD2626)
Variant Description: Infernal visage, coming apart at the seams. Suggested by Egoist.
Download Link: Brimstone (Lv5).zip