The graphic of Cleopatra, as it stands, probably would be found to be an infringing derivative work. (I say "probably" because nobody really knows what a judge will do until he or she rules.) You have several options here. Nobody can copyright the "idea" of Cleopatra or the "concept" of her. We are all "inspired" by the works we have viewed and read. Perhaps you could do a new graphic that would not use so many identical elements as the image you saw at the other site? Perhaps you could ask for permission to use the work? I'm afraid I can't really give specific legal advice because the reality of giving advice over the internet might subject me to liability for practicing law without a license.

Derivative works are a very tricky subject. Often, the original creator actually WANTS his or her work to be used to create derivatives. (For example, Gene Roddenberry was extremely happy that Star Trek fans wrote stories set in the Star Trek universe thus keeping the dream alive. It was the fans who pressured for movies to be made and for new television shows to be made. And none of that would have happened without the derivative works—both fiction and graphic.)

However, some creators become incensed if they even suspect that their work has been used as the basis for a derivative song, or story or graphic work. (Recent law suits by Disney and various music copyright holders demonstrate this very clearly.)

As a general matter, before AW would get into trouble for permitting a derivative work to be posted here, there are certain legal formalities that have to be satisfied on the part of the complainant. There is supposed to be an opportunity for the site to purge the offending work, if it is indeed an offending work. However, the better part of valor is to head off problems before they arise. When in doubt, ask the originator of a work if you may use it.