What awesome theme should I build my game around?

Hey all, I have recently been posting in BGDF and BGG for the last month or so, helping out people and so forth, now I require that you guys help me out with something.

I am making an awesome card game, that can be played within 40mins between 1 to 4 people that is fun as hell and with its solid mechanics and rigorous playtesting: it can be replayed a significat amount.

I will be making this. And it will be a heavy hitting game.

Scoring system is not yet established.
It [b] will [/b]involve: Champion Cards (like heroes in Warcraft 3), A Cyclic Engine (similar to dominions continuous card and deck management), Heavily Networked Node Cards (like Le Havres town cards that all depend on eachother), Parasitic Gameplay (like race for the galaxy's turn declarations) and finally "Win More Crads" (if you have been doing X, or Y throughout the game - then get more VP's).

I want to start the whole process out with a theme, and you need to tell me which theme YOU would like to play the most:

1) Steam Punk (heavy use of stylistic art and maybe brass cog meeples)
2) Atom Punk (Raygun gothic - similar to fallout series "retro-future": how the future looked from the 1920's)
3) War correspondant / Journalism (reporting for a newspaper)
4) Fantasy RPG - standard orcs, elves, giant rats and heroes and "the sword of blood +2"
5) Cavemen (travelling the lands, finding fire, developing society, attacking dinos)
6) Exploring/Cave Spelunking/Water diving for lost treasure
7) Space Cowboys: Firefly themes, cattle ranching, space ships and lasers, establishing new colonies, trading & salvage
8) Chaos Overlords: Dystopian Future where corporate companies hire futuristic gangs to rule their zones

Which theme would be the best for a 1-4 player card game that is fun as hell and easily replayable?