Buttons would need to be in
PNG format for still
APNG format for animated buttons
600 px by 600 px
You only need to upload images for the experience buttons that you will be using
Step 1 - Select your specific event and go to the section titled "App Experience" and select "Edit".
Step 2 - Select the option "Customize Experience Buttons" which will then open up the "Experience Button Customizer".
Step 3 - Hover over the button that you would like to customize, then select the cloud upload icon to upload your PNG or APNG. There is also a delete button to revert back to original Snappic button and the back arrow will revert back to the previous artwork that was uploaded. Once you are done with uploading your artwork for the buttons then you can click "Done".