It's a shame we lost these on the last board. Anyway, here's the names I have found in the Artbooks, though I'm sure to have missed a few, knowing me:

[EDIT]: Apologies, this has been posted before, but not "properly". At some point, my cookies went woowoo on me and I lost all my unread threads...

Characters:
Constantin Valdor (Chief Custodian)
Mikaelor Cobernus (Shield Captain)
Neron (Shield Captain?)

Squads:
Ares Guard (Emperor's/Valdor's personal guard)
Lentum (Foot Knights)
Artulon (Veteran Squad/Foot Knights?)
Ascetum (Terminator)
Argonus (Terminator)
Aquila (Assault Terminator)
Ballatoron (Tactical)
Aquillon (Guard/Tactical?)
Castason (Recon)
Apollus (Assault)
Trajanar (Bike)
Auito (Bike)
Fulman Cavalry (Bike)

Dreadnoughts:
Sagitarus
Senitoius
Primarus

Vehicles:
The Emperor's Gift (Skimmer Rhino)

If anybody finds any others, then just post them and I'll add them to the list.