When you're using someones' image, table or diagram you must have permission from the author to use it, or using a free image. You can find free images with Creative Commons licenses on different web sites.
In academic writing you cite and refer to others' texts, and this is absolutely acceptable according to the rules of copyright, as long as you follow the formal conventions surrounding citations and references. But what are the rules for using others' images?
If you want to use someone's image, table or diagram you cannot simply reference the source from which you took the image - you are also required to ask for permission to use the image from the author before including an image in your work. Of course, you must also provide a clear reference for the source of the image. To obtain permission, you need to contact the author or publisher (the party that holds the economic rights to the work). Permission does not need to be provided in any specific way - it can be either by word of mouth or in writing. Keep this permission!
If you want to ask for permission to use a figure from a scientific publication you can usually find a link from the electronic version of the article that takes you to a form where you have to state your purpuse etc.
Find free images with Creative Commons
If you want to use others' images there's a good way to find images with a free license.
Creative Commons (CC) is an international organization with the goal of simplifying the legal use and distribution of creative material on the Internet. By using so-called Creative Commons licenses the author of a work can mark the web-based material in advance and clearly describe what others can do with his work. For instance, if you find an image online with a Creative Commons license that allows you to use and distribute the material (with specific conditions) it’s basically the same as getting permission to use an item without the need to actually contact the copyright holder. You can find Creative Commons materials through a number of search engines, for example see Creative Commons Search.
When you find an image (or other media) with a license that permitts you to use it, it is also important that you refer to the image correctly. The SLU University Library gives suggestions on how to refer to images according to the Harvard system.