The logo in question is a copyright infringement of Siggraph. To use the design could possibly lead to lawsuit.
http://images.google.com/images?hl=en&rlz=1C1CHMI_enUS302US303&q=Siggraph+logo&um=1&ie=UTF-8&ei=LiqZSo2PIIWyswPpkNWpAg&sa=X&oi=image_result_group&ct=title&resnum=4hrhix, the Logo Tournament community makes every effort to keep contests clean of infringements and copyright violations. This is for your benefit.
I am sure you will be pleased with the final outcome of your contest.