That's fine, but listen carefully to Matt.....his comment to look at the strobist website will be very useful for you, maybe not tomorrow, but if your trying to pull off shots that you showed us, just a little bit of light from one or maybe two directions will only add to your photos, particularly since you need more....not much more, but some.

I would encourage you to borrow a flash or rent one that can be put off camera or if you can get something with a remote just to try, I think it will open the door enough for you to really start seeing what just a little flash will do to make those great photos of yours pop just a little more or add that sense of drama you already have even more.

Bob E.