"bust" makes an empty mask with a mannequin head wearing it
"mask on pole" is self explanatory
"mask stand" is similar to "mask on pole"
"holding mask" so far makes an image of an off-screen character holding an empty mask, the mask tends to be their own face but empty
There's also "costume on floor", "hung costume" and other tags I haven't fully tinkered with yet
Putting "(domino mask, masquerade mask, noh mask, diving mask, oxygen mask, sleep mask, surgical mask, sports mask, glistening eyes)" in the negative prompt can help remove the chance of it generating an occasional bandit mask or odd face patterns