Images such as portraits, maps, and infographics are especially important for presenting history. Online history has tools available for the historian who is not a graphic designer. Here are my favorite plugins for sites powered by Wordpress.
Getty Images: This plugin accesses the vast Getty library. As with images from Wikipedia, they are free to use.
ClickAnimate: This gives movement to both graphics and texts. I use it sparingly as too much movement on the screen becomes distracting.
CanvaKala: This is a mini-photoshop for images and text.
Enhanced Media Library: Allows you to organize your images. They can get out of hand really fast.
I am not an artist so using plugins are a real help for me. Moreover at the rate of a new post each day, I don't have a lot of time to spend on graphics. See the end results on History Moments: http://historyweblog.com/