Team Frog is GO!
Named them all after mythological frog/toad gods and beasts.
Seismitoad (Ch'ang-O, chinese toad in the moon) is a bulk master
Poliwrath (AnikaPeu, some Inuit Myth. Translates to "The Toad Master") For Phys attacks with a slight side of bulk
Politoed (Heqet, Frog-headed Egyptian goddess of fertility) Special Attack and a little bulk, also Drizzle for rain.
Lickilicky (Kci-Coqol,
http://www.native-languages.org/aglebemu.htm... This was a stretch... Lickilicky kinda looks like a Pacman Frog) HP and Phys attack, Dragon Tail for forcing switches.
Greninja (Jiraiya, Ninja that could turn into a toad in Japanese myths) Special attack speedster
Toxicroak (Paakwa, from Paakwa Kachina. Some Hopi native american stuff) Fast Phys attacks
Not necessarily the most competetive, but it's decent for a theme team I think.