I recommend the book The Visual Display of Quantitative Information by Edward Tufte (Graphics Press).
Although I don't demonstrate their use in this book, I want to mention two more full-featured graphics software packages that are free, and very useful if you'll be doing graphics to any extent:
ImageMagick and its Perl interface module Image::Magick is a valuable tool, especially for creating images. Over 60 different file formats are supported, compared to the much more limited number in GD. A wide range of image-manipulation techniques are supported, enabling you to create animation, thumbnails, and apply many image processing functions, for example.
The Gimp (GNU Image Manipulation Program) is very much like the Photoshop program. It has an interface to Perl scripts that is built-in, and there are several modules, starting with the Gimp.pm module, that provide Perl programmers with access to its functionality.
Between GD, Gimp, and ImageMagick, the Perl programmer has ready access to a host of image creation and manipulation software, at no cost.