When deciding on what race your character will be, consider what species are already aboard Tiberius...Some species are rarer than others. There are links below to help you research the possibilities.
These sites are also good resources for writing your posts, bookmark them. 
Current Species Played:Bajoran-
1 Brex (Counselor Margon's adopted son)
Betazoid-
2 half Betazoids (Doctor Peterson and 1 inactive: Admiral Quinn)
Bolian-
1 (Counselor Margon)
Cardassian-
1 (a refugee)
Daa'V-
0
Denobulans-
0
El-Arian-
Two half El-Arian characters (Lt. Commander Aeric James and Captain Quinn)
Ferengi-
1 (Lt. Galdar)
Hologram-
1 (Rori, the nanny for the Captian's children)
Humans-
8 full ( Darius Shane, Mrs. Dr. Peterson, Nurse Caine, Lt. D'Callan, Ensign Dunn, Ensign Marie Barton, Lieutenant K'Tan)
Klingon-
1 Klingon raised
human (K'Tan)
Orion-
1 half Orion half human (Cyra Fredrick)
Vulcan-
2 full Vulcans (Sevryll and Tolok), 2 half (Nevaul and Murynn)
Trill-
1 joined Trill (Doctor Ryla Drett)
Romulans-
1 inactive character (Admiral Talbot)
1 half Romulan half human (Ensign Shelby Daelen)
Nalah Jarok (NPC refugee)
1 Andorian-
Lieutenant Zremm
1 Risan
Ensign Herm
Follow these links (bookmark them as resources) to explore the races and other info available available regarding the Star Trek Universe:
http://www.startrek.com/startrek/view/library/aliens/index.htmlhttp://memory-alpha.org/en/wiki/Main_Page