It seems like everyone is complaining about the dull, emptiness, and brightness of the new theme.
It's best to leave the brightness alone, since as you said, the transition from a dark theme to a bright one is quite a difficult transition.
It also seems that the entire half of the background image is just blank and grey. So, possibly, the artist should add things such as little minecraft characters fighting. Ya know...doodles. That's better than blankness.
I suggest contacting the artist that made the background, to further improve the background and fill in the void spots.