Details, please. Tell us a bit more about your story, including why/how/by who they got posessed. Do you have any idea yourself on who they could be? Like should they be rare, common, strong? Should they have a high special defense, or should they all have something else in common, like be related?
Telling us might help you.
But honestly, you shouldn't need our help. It really isn't that hard to just choose eleven Pokémon. If you have nothing in mind, just surf through the Pokédex or use a random generator, as previously mentioned.
But really, can't you be a bit original and decide for yourself instead of having us spoonfeed you answers, just because you're lazy? You don't need our help to make every single little decision in your fic- after all, it's your fic, not ours.
Sorry if I seem rude- I'm just tired of constantly seeing threads like this pop up. Threads where the only purpose is asking for help with a character or something. ><
But just...think for yourself.
~Psychic