From what I have read about it, the textures can be at most 70% transparent, if more than that, the player who is using can be banned/reported for damaging your opponent's playability.
"Each texture needs to be clearly visible as not to give you any sort of advantage during gameplay" - Qubic.
If your texture gives you a massive unfair advantage then it is not allowed. You will probably get into trouble for this even if you have a texture which within the invisibility limit.