Looks pretty good to me, but the crystal details compared to the actual tail part is a bit distracting, maybe it should look like light is reflecting through them?
It would be cool if you made corresponding back crystals, to go with them !
One with a vertical pattern and one with a circular pattern
Summary
I do agree that the crystals could be better texture-wise, but as far as I know, Roblox still does not support any fancy maps like opacity, so they will have to remain opaque.
But I could try possibly doing a gradient or spots of lighter color instead of a solid color