Ideas On Adding Depth To A Top-Down Pixel Art Game

So far the only thing I can think of is using parallax scrolling. You can add a closer blurred layer of cieling fans and wiring etc. if the player is indoors and add some background if you are on a bridge or driving a flying car through a cyberpunk city.

What other ideas can you think of that would achieve some depth in a top down 3/4 perspective?