I usually do not have a problem with mirroring textures but simple variations can really lift your art to another level.
By adding asymmetrical items you will bring the texture to life. Maybe one of his horns broke off, simulating an epic battle.
Teeth are also never symmetrical, just look in the mirror.
I'm not saying this is bad, I'm just saying you can add a lot of life to this by doing simple variations.
On every symmetrical texture (mostly robotics) I do the last step will be adding asymmetrical items.
A logo, a broken wire, a scratch, dirt, additional armor and so on.
As an extra to making your texture look better, I think this is the most fun step to do.
I really enjoy freaking on my art after I'm "finished" with it.
Give it a try!