Flags are another thing I've been meaning to pick at - they haven't had much attention in the last couple of years.
A flag consists of a baseflag (V, |vv| or |vvv|) in a given color, a recolored pattern (which would be various stripes, quarterings, etc., to include the possibility of none), a fixed-palate midicon (of which there really need to be more - there's only 8 ATM, plus none), a fixed-palate topicon (if there was no midicon; choice of 18 or none), and an optional border (which are all the same except for color).
All these graphics can be found in NG's /graphics/flags/ folder. There's also some raw flag dump graphics I threw in there long ago with sterling Good Intentions to work on them really soon here. It wouldn't be hard to throw in some more stuff, either more involved divisions of the field and/or lines of division, ordinaries and subordinaries, or charges (i.e., color patterns, shapes, and icons). Digging through really basic heraldry references make me wanna mess with this again; there's some stuff that wouldn't be hard to do but could look rather striking. Plus, ofc, there's the more-recent Dominions flags to be cannibalized, sigh.
But long answer short, it'd be extremely easy to add stuff. You just need to add the new graphics to /graphics/flags/foo (where foo is the flag part in question), and then add a definition in the corresponding /data/flags/foo.txt file...