You can always slap on the generic:

All work, including (but not limited to) graphics, contained in this modification belongs to their respective owners - (insert real name, © 2007-08)
Then say thanks to Viking Horde and BKB. Simple. (That is if you've already asked them. )
Also, I don't believe anybody in this forum could be bothered to take legal action over something as petty as this. Not to say that your graphics work is petty. <_<