Another all nighter I did. It was considerably easier because of the same format I chose to portray these moons. I went with a template, then I took a spectrum sample of blue/ocean colors to determine the flags' primary background color. The lightest being closest, darkest is furthest from Neptune. These are the KNOWN moons of the planet, who knows how many more will be discovered in years to come.
Nearly all the small moons are named for sea/water/river nymphs, so it was easy to just find different stencils for mermaids. The only astronomical symbols currently for the moons are for Triton, Nereid and Proteus. They were created using the Neptune trident and the Greek letter equivalent mated to it. I used the same pattern using lower case letters for the remainder of the moons.
I edited out all the mermaids because I got so much crap from flag 'experts'.