Seko, i think some copper work might improve the landscape; just make it end a bit before the top building windows and add some dithering to the horizon lighter area
P.S. is your landscape routine vertical scroll ready? You will need it to be for latter levels;
plus if you need some hints how to speed up the rendering try to get in touch with Colin Vella or 10shu, they are working on Super Metal Hero on Blitz too