The Blues Archive houses over 2,000 blues posters donated by B. B. King, Jim O'Neal, the Rosebud Agency, and many others. These posters document festivals, album promotions, and more.
Not all of them have been digitized.
Finding aid: http://purl.oclc.org/umarchives/MUM01783/
Images from the collection (L to R): Highway 61 Blues Festival (1st : 2000); 10 Years of the Best of Blue Suit Records (date unknown); 1986! The Year of B. B. King (1986); Albert King concert at High Chaparral (date unknown); Blues Open Air (1993)