Four allegedly "off by one" PNGs
This was Gna! #24465 and also is the of my old -crap-nits remotely related to flags:
cuyavia.png 29x19 instead of 29x20 jaffna.png 29x21 instead of 29x20 keetoowah.png 29x22 instead of 29x20 vampire.png 29x21 instead of 29x20
The original bug report was triggered by an attempt to determine the predominant colour for all flags as far as they have a predominant colour, for the new (as of 2.5, IIRC) plrcolormode NATION_ORDER, but I dropped it as fundamentally flawed idea, e.g., "NATO blue" for the natives was just wrong.
The "off by one" observation might be also wrong, i.e., the four old flags obviously worked as they should, but all other flags use 29x20, and maybe consistency could be a good thing:
"jaffna.png"+"keetoowah.png"+"vampire.png": Sorry, we had to truncate this directory to 1,000 files. 1,846 entries were omitted from the list. Meh