I have a small collection of stock illustrations on iStock which includes a series of city skylines of places I have visited. Here are some of the drawings so far:
To download them or to take a closer look, please go to my iStock profile.
UPDATE (29 July 2016): iStock has merged with Getty images and they have changed their contributor policies in some significant ways over time (mainly removing a lot of the control you have over your own work and significantly reducing royalty rates), which has led me to deactivate all my images and I am in the process of deleting my account.
City Skylines