One prime example of this is the use of color banding to enhance contrast of monochromatic data. Low values will, for example, be translated into blue, medium values into green, higher values into yellow and highest into red. While this may make some features stand out it is still an inherently dangerous visual metaphor. I have actually heard a worst case scenario of this usage in connection with some colorized photographs of Halley's comet taken by a Russian space probe. It has a bright red core, surrounded by a green shell which is surrounded by a larger blue shell.
Some situations demand a schematic visualization treatment rather than a realistic one.
This typically happens when showing situations which simultaneously have a wide range of sizes or time scales as, for example, planetary orbits. Here, radii of planets need to be exaggerated so that they are visible on a solar system sized picture. Another example might be the representation of electron flow through a metal, where quantum mechanical effects are replaced with classical approximations. The danger comes from the crispness and mathematical precision of computer images. A viewer may think that since some parts of the image are precise, then all parts must be mathematically correct.