Finding images that work well in the landscape aspect ratio can sometimes be a challenge. Below are some resources for quality images that are large enough to meet the size restrictions of the feature slide image. Care should be taken to provide a photo credit when required.
There are many other sources for non-Duke images, such as Shutterstock (a pay service) and Unsplash (free, but may require attribution). A list of freelance photographers available for hire can be found on the Duke Style Guide website.