Images often have copyright restrictions and thus require permission to reproduce. In the online environment, where it is easy to copy and paste, err on the side of caution and try to only use images that are copyright free or have open licenses.
Finding copyright-free or open licensed images:
Want to use an image you found somewhere else? Look around the the image's originating website to see what kinds of reuse policies the owner has. Always link back to the original image.
Like images and photos, most charts, tables, graphs, and infographics are protected by copyright laws. However, the data itself can be freely used if you want to create your own expression of the data. Just be sure to give credit to the data's authors and link back to the data source!
2015 Public transportation spending by census tracts - Berkeley
Source: Geographic Research, Inc. (2011). Map with 2010 Consumer Expenditure Data retrieved January 26, 2016, from SimplyMap database.