Maybe I'll post my ideas for characters and setting up here when they come to me. I'm always happy to take suggestions, too (i r not riter).
Presently, I haven't come up with much more than that the plot will be based on Payload and CTF. As I stated in my first post, it will probably be something along the lines of "Wheel this cart of nitro over to this facility and bring back whatever intel you can find," but with much less ham in my fists. Trying to sneak a cart full of nitro somewhere seems really cartoony to me and sorta fits the vibe of TF2, I think. Plus, defending a cart of nitro will probably require a bit of tactical prowess (though it sorta comes down to "save or die" at that point, since 1 bullet can probably set off a whole cart).
As for characters:
Scout will probably be set up with a Force-a-nature equivalent (Device: Blast and Leaping), low toughness, and the Speed power.
Soldier: Haven't though much about it yet, but probably has some sort of repeater. Special weapon should be the Equalizer (Strike and speed power progression for every injury)
Pyro: Everything about this is still applicable in 1862.
Demoman: What you see in the picture. Experimental TNT slings. Not really sure how that'll work, but probably another application of Blast (area: explosion)
Heavy: High Toughness Score, experimental Gatling Gun (takes a round to set up and is immobile while in use), Drawback: Lower Speed
Engineer: Animate Objects. Maybe create the combat mini-sentries (how does boiled water discern alliances?). Maybe swap the Gatling gun to him and give the Heavy something else.
Sniper: 'Nuff said. Lots of aiming and sneak attack feats.
Medic: Probably uses some steampunk version of the medigun. Radiation from the device gives him mild regenerative abilities.
Spy: Disguise Kit is essential. Not sure about an invis-watch equivalent.
Also, I should probably give all of them awesome 19th-century names.