Those are looking sharp, you're a quick learner! As far as getting caught up on the details remember that even a battlemap is a map and not an illustration. Maps are made to give the information those using them want to convey, as such they don't need to give absolutely all the information about a scene. All your information seems immediately readable and clear and the maps fun to look at to boot. If you have time in the future and plan on doing a lot of broken glass the tutorial wdmartin did here could be used with the right texture to make broken glass (or scattered papers in an office) to augment the effect you already have. If you want to show your players the picture of the buildings but don't have a ruined version, just throw a grudge filter over the image and give it a boarder like an old Polaroid to make it look like a photo from when the city was intact, instant GM cheat!