The kludge that Poser uses (because it doesn't support the alpha channel of a .png) limits one to the use of jpgs. So, there are ways to use .pngs in Blender if you're willing to convert two images into one.

However, the above solution does work... adjust the gamma level to achieve the amount of transparency you desire.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks