Add a photo texture
Sometimes photographs help me to improve areas in a piece that I’m working on. Here I place a picture of a brightly lit car driving on a highway. I use it on a Lighten layer when my textures have saturated colours and if my background is dark, such as my dark blue that I’ve chosen here. I adjust my colours using the Color Balance tool until I’m happy with them.
Add effects to improve definition
The Halftone Pattern filter adds noise to an overly smooth illustration. I need to make sure that the pattern doesn’t contain too much contrast, which would be a problem if the image needs to be printed. I also use the Glowing Edge filter to adjust the halftone, and then change to layer mode to Lighten.