You're trying to balance lighting and exposure in a really challenging environment. In order to take a picture, you've got to have some light, and you've got to set your camera up to capture that light. One of the problems you're going to see here is that there's a multitude of changes you can make, some of which might include new equipment, and those changes will impact other aspects of your photos, but I'll try to give you some things to think about.
As I mentioned, your picture will be affected by the exposure of your camera and the light available while you're taking that picture. The light will be some combination of ambient light (the light that's in the room before you start monkeying around) and artificial light that you add for your purposes. The "while you're taking the picture" part is the shutter speed on your camera.
If you hold lighting constant, then setting your camera up is all about the exposure settings -- aperture, shutter speed, and ISO. I'm not going to get started on a full explanation of all of these, because we've already got some excellent discussions here on exposure, but if there isn't a lot of light in the room, it's very likely that you're going to want to use a large aperture (small f-stop number) and high ISO speed for these shots, and you'll want to understand the impact you'll see on depth-of-field and noise in your photos.
If, on the other hand, you want to start adding light to the room, things can get complicated in a hurry. If you imagine walking into a dark room and flipping on a light switch, that's going to change the light level in the room (obviously). The good news is that there's now more light available for you to take photos, but the bad news is that you've gone and completely changed the nature, direction and white balance of the light in the room, and everything looks different now.
If you haven't done so already, I'd pay a visit to the Strobist web site to start getting a sense for the sort of flexibility and control that are available with artificial light. You might find that it takes some work to achieve the look you're going for, but you might also find that it helps you think a little more deliberately about lighting (where it's coming from, how it's spread or diffused, etc.). We tend not to worry about that very much when we're shooting with ambient light only, but once you start to train yourself to think in these terms, I think you'll find your ambient-light photos improve, too.