I like to create the illusion of space on a 2 dimensional support. Artists can achieve space with a number of techniques. I previously wrote about linear perspective. You achieve atmospheric perspective by lightening and dulling colours in the background; using a bit of blue and reducing details. Body position is also helpful. A figure with the back toward the viewer or a look in a particular direction helps create the illusion of space. Overlap of objects is a wonderful technique. These are just a few techniques an artist uses to create the illusion of space.