High Quality Transparent:
High Quality -
good resolution & clarity.
clean and quality art. (close to original as possible)

Transparent-
No background white or translucent. or:

multi layered images where the background can be removed. Or easily editable images such that the background can be removed without much effort.

General /e/ rules ofc, if possible getting different levels of ecchi is extremely prized (clothing on, clothing mostly removed / scantly clad, nude)

Thanks for sharing.