
Explanation
Graphical user interface, text, application Description automatically generated

Box 1: Screen
You can add an image to a screen in several different ways. One way is to upload an image to the app, go to the Media tab, and then click on the image to add it to a screen.
Note: Configure graphical elements in your app, including images, photos, and elements of a pen control.
BackgroundImage - The name of an image file that appears in the background of a screen.
Applies to the Screen control.
Box 2: Screen
Out Of Box Canvas App, provide a property called LoadingSpinner and LoadingSpinnerColor.
LoadingSpinner property is used to displaying a Canvas App OOB Loader Image unless your screen finishes loading.
Click on the Screen in your Canvas App and then You'll be able to see LoadingSpinner and LoadingSpinnerColor Property.
Graphical user interface, application Description automatically generated

Reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/controls/properties-visual
https://arpitmscrmhunt.blogspot.com/2020/04/powerapps-display-loading-icon-until.html