I agree with Elliott: your game has a great look, and your wiki does too. In the distant past I used YouTube to show my artwork (and some rough Unity game scenes), but that was before I had a good camera or any idea of what I was doing. Somehow, even with my amateurish low-res videos, I got contacted by someone who had a medieval crafts and games website, asking if he could embed one of my paper castle vids. I said, "No way!" I mean, I said, "Sure!" That move alone greatly increased my views, although other factors in my life (bad decisions on my part, mostly) pulled everything downward again.
My current project heavily involves YT and Vimeo video as actual parts of the game play, so in a sense I'm using YouTube for both marketing and as part of the game. Maybe you could use YT videos to hint at Easter Eggs hidden in the game, or something like that...
Yeah I definitely agree YouTube videos are useful. A single, simple video trailer can go a long way. You can use it for all marketing efforts: App stores, any media mentions can link to it, it can go on your wiki / webpage, can be used for a kickstarter etc.
It should feature some gameplay, some concept art, music, sfx, game logo. It doesnt need to be super complex to be effective.