street:
https://opengameart.org/content/faux-asphalt-texture-pack
license:
public domain

car:
https://opengameart.org/content/free-top-down-car-sprites-by-unlucky-studio
license:
Created By UnLuckY Studio
You are free to use it in your commercial projects. If you have any suggestions or questions, you can log on to www.unluckystudio.com

skyscraper:
https://opengameart.org/content/skyscraper-textures
https://opengameart.org/sites/default/files/skyscrapers_20110801.zip
license:
CC-BY - Donation by hackcraft.de, generator by Benjamin Pickhardt