The above link amply explains the difference between the two Elder Signs, which is the more familiar star-shaped Elder Sign created by August Derleth versus the one sketched out by HPL. To make things ever more interesting, Lin Carter tried to reconcile the two. Which one are you using in your campaign? Please note I am using images from the site and have no control over the relative size of the images.
Elder Sign by Derleth (below)
Elder Sign by HPL (below)
Elder Sign by Lin Carter (below)