Cryptic has done a great job adding in off-duty uniforms and expanding the list of hairstyles. So let me say "Thanks for listening to the community" to our devs. However as you guessed there are always a few more things that can use to be thrown into the mix.
Lots of things could be done with off-duty wear such as:
More variety in the cut of the clothes. For example, regional dress like kimonos or saris.
Skirts in miniskirt, knee and shin lengths.
Short sleeve shirts. (Everything is long sleeve except for the female MU tops. Is their a taboo against showing elbows in the future?)
More patterns to be used on clothes other than vertical vs diagonal strips, such as a floral, spiral or lightning bolt motifs as examples.
Logos we can add with similar size-location-rotation options as scars and tatoos. Designs could be the different emblems from the series (example) and / or the sort of generic images used by many teams (Tigers, Cowboys, Rockets, Stars ... etc).
Possibly a nice "see-through skin" option for aliens like the Gallamites.
Lastly, yet more hairstyles such as the Long Curlled female hair in Champions (or like Elaan had), a mullet (for those captains that both party & business), mohawks (just incase I want to play an Iroquois warrior), and long hair of varying lengths (e.g. should & mid-chest) that comes in both the well-combed and wild variety.