My idea is for the Timeline widget in Experience builder to support Image Service as a data source. The Timeline widget currently supports map services, but not Image service. If I try I get the message "No added data can be used. Please add data."
The Time slider in Instant app (Slider template) and in Time slider widget in Web AppBuilder handles the Image service without any issues.
In my case it would enable me to use an Image service with historical aerial photos together with a time slider, which in Experience builder would be used to compare older and newer situations with two maps (connected by trigger+action when extent changes) side by side. Currently, I would have to embed the Instant app, but it will have no connection to the other maps and functions in Experience builder.