Abstract: An underestimated and time-consuming activity for researchers involved in image processing, computer graphics, display quality analysis, and perception testing is the preparation of a good set of images to be used in the experiments. These images not only need to fit specific technical requirements, but also need to be free from licensing and copyright issues. In order-to-provide easy-to-use solutions for a wide range of testing needs, we developed the TESTIMAGES archive, a huge and free collection of digital images designed for analysis and quality assessment of different kinds of displays (i.e., monitors of different sizes, projectors) and image processing techniques. The archive includes several million images originally acquired and divided into four different categories: SAMPLING and SAMPLING_PATTERNS (aimed at testing resampling algorithms), COLOR (aimed at testing color rendering on different displays), and PATTERNS (aimed at testing the rendering of standard geometrical patterns). The TESTIMAGES archive can be freely downloaded from http://files.testimages.org and used for practical tasks such as monitor calibration and shader testing, as well as for scientific research.