Is your source recreating a form that is already very common? Then you don't need to cite it, as you could have taken it from a dozen other places and it would have looked the same. You might want to search for the original invention of the representation, although if it's very common this becomes somewhat exaggerated (I cited Mollweide (1805) for the Mollweide projection, but most people wouldn't).
Is the representation that your source uses a new one? In other words, is it original work created by the author of your source? Then you should cite/acknowledge it or you might be accused of plagiarism or even copyright violations.
When in doubt, I would cite the source. If you cite where it wasn't really necessary, consequences are minimal. At worst people will think “why did she add a citation for something trivial/obvious?”. However, if you fail to cite where you should have, consequences could be quite severe.