You should have put some book characters in like Uriel Ventris, or

high marshal helbrect.(Well theirs a figure of him but still)

CAIN! Ah-ah! Hero of the Imperium!

By the way, the song with the distinctive line "Stop. Hammertime!" is actually called "U Can't Touch This."

Speaking of which, maybe the nine loyal Primarchs could perform "2 Legit 2 Quit"?

But the Tyranids are unforgivably absent! They could sing "Nom Nom Nom Nom Nom Nom Nom" by Parry Gripp.