@JeffreyDaro
To save the daily quota,
Specify the album to scan, not whole or many albums. Scanning will consume your Quota, And the number of files in target albums will also affect consumption.
You can only show 8640 pictures in a day at most, even with 10 seconds. With 60 seconds, you can show around 1400 pictures per day. If you have thousands of pictures in the album, unused pictures would also scanned. (scan 50 pictures would consume 1 call) It could be more efficient.
Let’s compute: If you have 5000 pictures in your target album, you will consume 100 calls per scan, and to serve each image, at least 1 call per image would be consumed. But most of the scanned pictures would not be used at all.
So, optimise your album. Carefully collect/select pictures to be shown with a proper number. Gather the pictures in one album like 'MM Wallpaper". Keep the number as low as possible, and assign longer updateInterval as some minutes, not seconds. It will help your quota consumption.