This article shows you how to customize the appearance of your iPhone app icons in iOS 14 using photos from your Camera Roll and the Shortcuts app.
How to Customize App Icons on iPhone (iOS 14) | Kayla's World
In iOS 14, there are a lot of things you can do to customize the look of your Home screen, including changing the images on your app icons. You can use any images you have in Photos. Some people like to find a set of images they like and customize their phone based on those images. If that’s your preference, start by deciding how many icons you want to customize, find enough images so that you have a different one for each icon, and then follow these instructions to customize those icons.
Open the Shortcuts app.
Click the + (plus) icon in the top-right corner of the Shortcuts app.