I wrote an article in my blog about one of the tricks I use to add dynamism to static pre-rendered backgrounds. Making them a little bit more dynamic helps to express the intended mood for that room better. Please check it out! English is not my first language so I hope it is easy to understand.
http://bumpytrailgames.com/2017/10/06/dynamism-static-backgrounds/
It's pretty hot in here isn't it?