If you want my comments:
The poster would look perfect as a long poster, turned vertical.
I would just center the great illo in the middle, nix the castle stuff, and put all the show date and club info on the bottom, just as you have it. Then, on top above the art put the names of the bands (which you are missing Devil-tones and Runarounds.
It would make the poster more striking, and really draw out your illo art better!