CrunchGear has posted the first banners at WWDC which promote both "OS X Leopard" and "OS X iPhone". The "OS X Leopard" banner reads "The world's most advanced operating system," while the "OS X iPhone" banner reads "The world's most advanced mobile platform."
Additional photos from the Flickr photo set from Gernot Poetsch. Another photo posted on Flickr shows a large Apple logo in Moscone as viewed from the W Hotel.
Update: MacNN has posted an extensive gallery of images from Moscone: