I don't know some of the mentioned characters yet because I am about to begin Mission Gamma pt. 2
Elias Vaughn - I actually view the dude on the covers. The model they picked fits perfectly for him I think.
Prynn Tenmei - Jennifer Garner - definitely not Rachel Luttrel
Shar - I don't really have a Shar - the model is a bit to kid like for me. I picture a twentyish effeminate male.
Admiral Akaar - I completely view him as the Akaar on the cover of Red King. That stony face is perfect.
Taran'atar - I can't really see an actor here, I just have a deep voiced Jem'Hadar in my head
Treir - Tricia Helfer with green skin...