[B&H] Allow gallery tattoos to be imported as a layer rather than overwriting

There is so much potential for the Create-a-Tattoo feature, and there are already many beautiful and creative works on the gallery. Why can't we layer multiples of these works? In my opinion, this is a very odd decision to make and restricts some of the creative freedom that the tattoo painter provides. 

I am sure there are many other examples, but in my case I would like to be able to have multiple different skin detail tattoos on a sim, but I am left disappointed at being unable to do so.