It's just amazing what a single small pocket flashlight can do with images, instead of using onboard flash. One evening I was taking pictures in a dark room. My "model" was a small alcohol glass. When I shoot on tripod, I always use manual focus in liveview mode active. This time the room was so dark that I couldn't see anything on the screen in liveview mode. Despite using autofocus and onboard flash for helping camera to focus, I took out a small flashlight (not a led one. Regula with yellowish tone) and pointed the light from the top to the subject. And when I saw the result in liveview, I decided just to stay on that lightening. The result came out totally different of that what had came out using onboard flash (i don't have wireless flash set up, however, i have one external flash). The picture isn's so "flat" and there's no big reflection on the front side of the drinking glass.
So, all in all, if you've used onboard flash so far, try something new. And a cheap little flashlight for the start is totally OK.
Once the picture was taken, it was time to boost up the effect. What I did with those two pictures here, I turned them to black and white using a layer in a program. I used a black and white layer which let's me control the darkness/brightness of each color. In the end I had a BW picture with desired contrast level. Now, as black and white still seemed too boring, I cut a hole into BW layer to bring colors out. Then added a curves layer in which I made the linear line a little more like S-type to boost up contrast/brightness again. The final result came out pretty nice - great lightening and nice beautiful colors.
Have fun on experimenting!