Here's how to make a photo into a dial wallpaper of an Apple Watch:
In the version of Apple Watch OS2.0, you can use your own photos as the desktop background. Before you start, you need to set it up on the paired iPhone. Please open the Apple Watch app on the iPhone screen first.
After opening the Apple Watch app, please click the photo bar option in the list.
Since the pictures on Apple Watch are synchronized from the mobile phone, you need to select the album to synchronize here.
As shown in the figure below, here are the photos from my personal collection on my iPhone.
Then, after the photos are synchronized to Apple Watch, use the previous method to enter the dial replacement interface and select the thin dial.
When finished, you will see your photo on the dial of Apple Watch.