Here is the casting of additional characters. This may change as new characters may get added. These are visuals that I picture in my head, you can use these too or you can imagine your own visual for different characters :)
Feel free to come back and refer to these characters along the way as you read.
Also I do not own these pictures, I just get them from google.
Stephan (Luna Eleanor's beta)
John
Alec
Eric Northman (Vampire King)
(Might change later ^)
Ben (Kian's best friend)
Cody (Nick's best friend)
Martha (The dark witch)
Mark and Helen (Lara's adoptive parent's)
Paul (member of the werewolf council)
Let me know if there are any characters you would like me to choose a person for :)