you could also try promoting in SteamGifts Forum.
people love Puzzle giveaways.
such as Its To Hard Puzzles.
they get lots of attention in the Forums to try & solve them.
ya, you might have to give a game away to get the promotion in there but its a HUGE community.
if you try this idea, i suggest constantly bumping the thread so it gets more people to see it.
you might try doing questions on metal trivia, there are alot of metal heads in that community.
ask people to pay it forward if they like the music, by telling their friends about it, in return for entering the giveaway.
another way at getting the word out is promoting the giveaway in Gamespot, IGN, & other gamer forums to get attention to the giveaway to get word of mouth to more people.
if you do this, keep the giveaway open for 2 weeks or so to spread more word of mouth in forums to get more people to check it out
Cheers Death2Videodrome, but the GA ended already - I'll be sure the guys in Pantheon see your ideas though.