I noticed a Springshare Support Blog entry called “No Cover Art” Placeholder Images for Books providing urls for images to be used as a placeholder for books that do not have an image available. There are two images available, both in two sizes.
There were a few books I wanted to add to my LibGuides, but decided against adding them because they did not have an image. (It looked funny when placed in a list with other books that had images.) These placeholders are handy. Here is an example of how one looks on my Women’s Studies page.
FYI, I noticed this support blog entry after logging in to LibGuides and reading the Support Announcements on the left.
You can usually find cover art at Open Library. Here’s the image for the Michele Wallace book on your guide.