Just writing down random tidbits as I find it:
The filename for all of the CG images from the first few stages starts with ICECREAM for some reason
I don't know if it carries over to the suffixes from the pilot IDs, but _F seems to be for face portraits and _B is for full body portraits. _S does appear to be for pilot suits/alternate sprites.
Looks like assists will get fancier images (see pic) once they level up, but I think we already knew that?
Obviously a lot of battle background assets but I haven't spotted any that didn't appear in the demo yet
pid_MINA does match the filenames for the gyaru girl on A.Advent
There's a lot of generic mob NPC sprites, probably for stuff going on on the ship.

Still digging