Some CC on the images.
1- I would shoot in tighter, much tighter. As with portraits, the importance is (usually) on the faces, the eyes, the emotion. In this image, I see no eyes, nothing. There is alot going on in the image and none of it is really of interest. I would of deleted this image (or probably not taken it). To improve, look for a vertical shot of the guy in the front, playing with the light coming from the upper left hand side. You would at least be isolating a single subject. Waiting for him to turn slightly to the right would get a bit of that guitar in the frame as well.
2- Same as with #1, not much of interest going on in the image. I do love how they are synched in their leaning back. Zooming in closer would of helped (or crop) to focus the subject of the image. I really do like the silhouette style light on the guy in the front. I'm picturing just that, with the blueish smokey back all around. That would of made a sweet shot.
3- This is my fave of the three you posted. Why? Because there are faces and emotion! You see not on the intensity on the front most guy but also the quirkyness of the guy in the back. Again, working at isolating a single subject is probably a good idea. If you want multiple people in the shot to show the interactions between them (which is great), a different shooting angle, usually more from the front, to put both subjects on "equal plane" in the image.
I really do not mind the noise at all, I actually like it in this image. Noise can add a certain element of grit to the image, but you need the right expressions and lighting, which I feel you have in this image.
I disagree in that these are wonderful. Sorry. The first is a delete for me. The second shows some really nice promise in terms of composition and imagery, but you need to worry about everything else that is present in the frame. The third is a pretty strong image, I like it.
For a first time concert shooter, good job. You can shoot a show in a very journalistic manner, which can be very boring very fast. You can shoot a show in an artistic manner, which is really fun but really challenging. The "rules" of photography apply, what makes a good shot and so on, and you add to that the challenge of low light, constant movement, changing light... which is why I love shooting shows.