Masks for Art?

[Shinzy]

Halloo!!
So I figured out how the Rule packs works now. And obviously the first thing I do is "Let's make story books as art! woo!"

the only problem is that I wanted to add a mask for one of the random texture sprites
and it does work! but the mask texture also gets rolled in occasionally, as a sprite for the art (see attachment)

can I get it to somehow not do this?

[attachment deleted due to age]