[Uniruler]

Can I use my terminator vet sergeant to represent a librarian in terminator armour??

 

[ArchonAstaroth]

Yes. Just paint him a little differently than the normal terminators and add some extra bits.

jwu

 

[Cheredanine]

Depends on the game, in an official tourney the rule is usually that all wargear must be represented, so you may str5uggle with the psychic hood, but otherwise, provided you make it clear to your opponent, this should not present a problem. In less informal games, it is a matter for agreement between yourself and your oppo, unless he is particularly beligerent it should not present a problem