Placing streetlights is a good example for that kind of work. It takes like forever, but you won't see a big difference, until the night comes and a hundred spots of light appear in the city. That really adds to the atmosphere!
However, I haven't just spent my time placing streetlights. Here are some screenshots from Randalls and Wards Islands, which I am currently working on. You will find a lot of public sporting areas there, but also the wastewater treatment plant. Nice combination, isn't it?
I hope you like what I am coming up with and you still don't lose interest in this project!
Regards
Horus