As of 2013 there have been three North American Disc World Conventions.
The first was in Tempe, Arizona in 2009. Pictures from that convention are here.
The second was in Madison, Wisconsin in 2011. Pictures from that event are here.
The third was in Baltimore, Maryland, in 2013. Pictures from that convention are being processed but here are some that are done.

Video clips:

2013 Masquerade (2:33)

2013 Banquet (18:14)

Baltimore July 4 Fireworks reception (23:36)

Baltimore July 4 tourist video (1:27)

Baltimore July 9 Touring inner harbor and Fort McHenry(15:29)

Baltimore July 10 Touring inner harbor and science center (2:54)

Baltimore July 11 USS Constellation Cannon Firing; schools of fish eating at the surface; Stern Wheeler (3:25)

Baltimore July 12 USCGC Taney, the last survivor of Pearl Harbor