All right, now here's the thing with Ancient destroyer; her demon form(A.D demon) and her princess form(A.D princess) are very similar. So, tagging fan arts of them appropriately will be a bit tedious since it's a bit difficult to put their identity in place. It'll be like the advent of Seaport water demon.
I can think of two ways of deciding whether or not whose who, by observing small details or reading up the artist tag.
As for the former way, you can't trust on the artists to always depict A.D princess with damaged clothing and A.D demon with proper clothing, mind you. Pornographic depiction of them will emerge sooner or later. So, I think you can differentiate them through few key differences:
*A.D Princess has longer drill hair. *A.D Princess has longer side hair (way longer than her face) and she let her hair down as opposed of A.D demon's tied-at-the-back hair (or short, I assume it's tied, judging by the CG). *A.D Princess has a white ribbon?(proper name, please) tied around her right armpit to her midriff. *A.D Princess's heels has silver/grey lining. A.D demon has black lining.
*In comparison in terms of their armament, A.D princess's abyssal cannon is primed with its lower jaw and main barrel. Not to mention it also has additional side guns. Whereas A.D demon's abyssal cannon has its lower jaw inwards and it looks dormant.
With that said, in this image, it should be A.D demon as oppose of A.D princess.
OR we could merge the tag together into "Ancient Destroyer Oni/hime" and be done with it.