You can add an image to Ambient Experience after selecting it. This feature is exclusive, at the time of writing, to Fire TV Stick 4KMax and Omni televisions. You can also provide feedback by clicking on the thumbs up/down button next to each image. Amazon Photos allows you to access your images from any device.
Amazon’s Titan Image generator powers the whole thing. This is an official preview, so don’t be surprised if at some point you see something strange. Otherwise, enjoy.