Add a cool tone
A tonal change at the end of the project will help to make all the separate elements look like they belong together, and a slightly desaturated, filmic look is ideal for an effect like this. A great place to do this is in the Camera Raw Filter (Photoshop CC only). Once everything is in place, hit Cmd/Ctrl+Shift+Alt+E to merge layers, then go to Filter>Camera Raw Filter. In the Basics Panel, add Clarity and increase the Shadows. To give it a cool tone, drop the Temperature to about -10 and then increase Vibrance and decrease Saturation.