Here are some Debian related diagrams and sketches, please add more. Graphs and other statistics should be added elsewhere.
Debian development process (new src, old src old Spanish src)
Debian buildd, wanna-build systems
Release timeline, another release timeline, General timeline
Debian package cycle, also on Wikipedia commons
apt state files (src 1 2)
BTS system (from DebConf17 debbugs)talk
Debian Fun Statement infographic
See also: