Either pay outright or a raffle to have the privilege of naming the next outpost if games go to 12 players or the new specialist.
maybe a raffle to decide what the specialist will look like etc. I could see spending a dollar to get my chance to put my mark on the game. its passive.
this kinda falls into the selling alternate art, but on a grander scale because your buying a chance to design or influence the art. i think a lot would like that. as long as it was inline with the games theme