Icons are a great way to break up large blocks of text, and to draw your reader in toward important information.
The Noun Project is a great resource to retrieve free, royalty-free icons -- just search for any noun (ie: "yarn", "library", "lightbulb"), select the icon you want, and download! The images come with the citations pre-included, so there's no worry about giving credit.
(Glasses icon by Rigo Peter from the Noun Project)
Iconfinder is a free program recommended by Librarian Design Share. There is also a premium version but the basic is free to all.
To find icons using a Google Image Search, try the following: