I don't have 6,000 stills (yet), but have cataloged almost all of my Japanese monster stills now.
Highest total for a single film - 171 (for the 1954 Godzilla).
I am a little over 2,000 for the Godzilla series in total (mainly a combination of Japanese and U.S. stills), and over 3,000 different including other Japanese giant monster movies.