In the 90's many "posters" were simply advertisements in local papers, flyers, ect. Any other official posters that could be purchased were generally as part of a festival or event DMB was part of.
In 2003, Steve Keene created a series of art which was used for various venues through the Dave & Tim and Summer tour.
In 2004, there were various artists used for posters. The Dave & Friends tour used artwork from AJ Mapes, which was used for many of the shows. For the Summer tour ...