An image element displays a single image. Although you can supply images in any format that iOS supports, it’s recommended that you use the PNG format.
Supply images that look great on all display sizes. You can use a single image resource for all display sizes as long as it maintains clarity. For guidance, see Autoscaling PDF Images.
Create images at 2x resolution. Apple Watch has a Retina display, so there's no need to create standard resolution images. Include @2x in image names.
Avoid overlaying text on images. Putting text on top of photos or graphics can decrease both the clarity of the image and the legibility of the text.
Use placeholder graphics to reserve space for an image while it’s loading. A placeholder graphic is a visual cue that an image occupies a specific location but is not yet ready to be displayed. Placeholders let you load your interface quickly and still have the time to prepare the images you need.
If you need to use WatchKit to animate a sequence of images within an image element, see Using WatchKit Animations If Necessary. For tips on how to optimize your images, see Image Optimizations; for developer guidance, see Image (SwiftUI) and WKInterfaceImage (WatchKit).