Use the following guidelines for images:

• Landscape format: Use and take photos in landscape format, see figure 1. This will enable the user to see more of the page as they are looking at the photo. If you have a photo in portrait consider using the guide: From portrait to landscape format.
• Full resolution: Upload the photo in full resolution, if it is an illustration, then make it as large as possible, preferably around 2000-4000px in width and height.
• Full width: Let photos and illustrations be full width. This will them easier for the user to see, and it will create a consistent look with aligned left and right margins.
• Watermark: Upload without a watermark. WordPress will automatically add a watermark to the image, see figure 2.
• Rectangle: Illustrations should be uploaded as a rectangle. WordPress will present the image with rounded corners.
• Stroke: If an illustration has a white background and the subject of the illustration is cut off, then it often helps to add a stroke around it, to make it feel part of the content as a whole. There is a guide that shows you how: Add a stroke to an image.