Some ideas that are kinda already mentioned but maybe not as blatantly…
1. Stream the game constantly. I would desperately try to get up on Twitch and similar listings with viewers. You will gleam a bunch of viewers just by being on the list and hopefully, generate a bunch more players. The game is cool and the more you make the list, etc the better. I am sure many players would help out as well to ensure there is constant streaming going on always. The game is very solid and looks very cool. Once people see it, hope for the best. Lots of people would buy the game after seeing the stream, or at least I would.
EDIT: Is there a way to add a streamers list to the website? Or at least direct them?
2. Take full advantage of Steam. Work the hell out of how popular it is. I am unsure why you don’t have it up yet, I am sure there is a good reason. However, when you DO get it going… figure out how to make that front page set and milk the crap out of it.
If it needs to be DLC to make the front page Steam news, find out the min req’s to make it to the front page with a new one. Even if they are not huge. Each time you add a map or mode, if it gets you to the front page again with a cool expansion name. DO IT. Your game is well priced and better than most of the crap that hits the steam front page a good chunk of the time. Just getting your name out will do wonders.
3. I agree with Goat’s idea of artistic DLC. The system makes money, period. People will pay money to have their helmet recolored. Its just true. There is too much money there to ignore.
4. See if there is a way to work into the TF2 system of “Play X game and get a TF2 item”. Just getting people to play your game for that item should help if its possible. I dont know how you do it, but i know a bunch of horrid games that you can play and get a fuzzy hat in TF2. If your weapon/item was very cool, I could see it generating revenue
5. Try to generate some Reddit traffic and similar. At least get a page going. You could just start posting some of the better videos of kills, funny, whatever and see if that sparks anything. Its a greater than zero, it couldnt hurt.