"Visual literacy skills equip a learner to understand and analyze the contextual, cultural, ethical, aesthetic, intellectual, and technical components involved in the production and use of visual materials. A visually literate individual is both a critical consumer of visual media and a competent contributor to a body of shared knowledge and culture (Visual Literacy Standards Task Force, ACRL, 2011)." - International Visual Literacy Association
Make sure your visualizations contain images that are free to use. The links below offer a number of royalty free images.
Government Organizations (such as NASA, NOAA, CDC/Public Health Image Library, Department of Agriculture, etc.)
University Digital Repositories