Wikipedia articles generally have a high density of images, typically 3-10 per article but sometimes as many as one per major section. Wikipedia's images are usually of high quality and covered by a free license. This tutorial explains how to find good articles to illustrate your article, using "vaccination" as an example.
The preferred source of images for Wikipedia is the Wikimedia Commons, which vets its images to ensure that they don't violate copyright laws. The Commons does not allow "fair-use" images, which are allowed by other Wikimedia projects, including the English Wikipedia. Therefore, your goal should be to find an image for your article on the Commons.
Mayflower search engine
editThe Wikimedia toolserver offers an image search engine called Mayflower
whose front page looks like this:
For illustration, a search for "vaccination"
yields the following results
Restricted Google Images search
editAnother approach is to search Google Images restricted to the Commons. Here's an example
which will produce something like this:
It's easiest to follow the links that say "commons.wikimedia.org" or "upload.wikimedia.org". You can follow the others, but you'll need to work out the name of the image to find it on the Commons.
Searching the Commons directly
editYou can search the Commons directly by following this link
This will take you to a page similar to the following image:
Typically, you will type your search string into the bar, and click on the adjacent button labeled "Advanced search". Prior to clicking, you may restrict the search of the Commons to various "namespaces", as shown above.
Searching by association
editAnother approach to find images is by association, that is, to search the categories of related images. For example, to find images for "vaccination", you might begin by searching the categories on the Commons for the images found in related articles, such as public health or polio or smallpox. To arrive at the Commons page for those images, click on the image in the related article, which takes you to its English Wikipedia page. Just below the image, you may see a grey box saying that the image has a counterpart on the Wikimedia Commons.
Click on that link and then click on the Categories at the bottom of the resulting page. You should see a wealth of images in each category, some of which may be appropriate for your article.
Other search engines
editOther search engines have been developed to search Wikipedia's images. Examples include: