Music guests would be a great idea, because no one has done this yet!
O.K. here are my ideas
Gabriella Cilmi
Sheryl Crow
Olivia Newton-John
Sophie B Hawkins
Juliette Lewis
Brian Wilson {Beach Boys}
Barry Gibb {Bee Gees}
Robin Gibb {Bee Gees}
Paul McCartney
Ringo Starr
Paul McCartney still does signings, but not at Collectormania - and you have to arrive at about 6AM {at the latest} to have a chance of meeting him. I know, I did it! Also I wouldn't call Phil Collins and Ray Davies realistic either!