I can see why guys are being critical. The linework is excellent (albeit lacking line weight variety) marred by composition that could be improved.
My comment would be the work is generally competent but not very exciting. And considering covers are supposed to be exciting, i would personally rethink the composition at the concept stage rather than trying to fix it in parts. This scene could be drawn from multiple angles and a good exercise is drawing thumbnails to see which angle is the best, rather than jumping straight into drawing a detailed piece.