An image element displays a single image or an animated sequence of images. Images may be in any format supported by iOS, but the preferred format is PNG. Animated sequences can be started and stopped programmatically.
Size images for 38mm and 42mm displays. You can use a single image resource for both display sizes as long as it maintains clarity.
Create images at 2x resolution. Apple Watch has a Retina display, so there is no need to create standard resolution images. Include @2x in image names.
Use placeholder graphics to hold space for an image while it is loading. A placeholder 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.
Optimize images. Strive to use images that are small and efficient and still achieve the desired goal. For tips on how to optimize your images, see Image Optimizations.
For developer guidance, see WKInterfaceImage.