apple-device-images

https://img.appledb.dev/[email protected]/deviceIdentifier1,1/0.ext

Replace res with 32, 64, 128, 256, 512, or 1024 to get an image which has a maximum horizontal or vertical pixel count of the respective value.
Replace deviceIdentifier1,1 with the device you want an image of, e.g. iPhone14,2 for iPhone 13 Pro.
Replace ext with the file format you want. The file formats available are png, webp and avif.

To get an image with dark mode, append _dark to the filename: /0_dark.png
To get a different colour, increment the number of the filename: /1.png

In the future I will publish a JSON with the site which lists which devices have dark mode, and how many colours each device has. For now you will just have to look.

Example images

https://img.appledb.dev/[email protected]/MacBookAir10,1/0.png

512x293, Space Grey, light mode

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https://img.appledb.dev/[email protected]/iPhone14,2/3_dark.png

127x256, Sierra Blue, dark mode