"the practice of taking someone else's work or ideas and passing them off as one's own."

Now, if you're trying to sell this artwork, it's plagiarism. If you're wearing it, it's not necessarily plagiarism if the artwork is royalty free (aka anyone is welcome to use it).

I don't think there's any specific rule on the forum for using some artwork from online as a head texture, but I may be wrong. I'm sure a smod would be able to give you a definite answer.

If you're just wanting to be safe though, be sure to check any copyrights on the art. If you're 100% sure rthat the art is free for anyone to use, feel more than happy to wear it my man. If you somehow mess up, no one's hear to bite your head off (except maybe skul; he might bash your skull in); I'm sure if any mistakes are made they can easily be cleared up. (: