Oh most of us that change it so often make the icones ourselves.
If toi ever find an image toi want to be an icone I could always make it for you. XD Ive made probably near a thousand ou so icones par now. I really enjoy making them
But essentially toi chercher up whatever toi want an icone of, toi find an image that toi think would make a good icon, take it to some kind of editting software (or paint if toi dont plan to do much to it), and at the very least, crop the image to be the size toi need it to be (square)
toi can get plus creative with it the plus your practice too
I usually used
link to éditer and crop and all cause its like Photoshop but online free and has no downloads. Not as good as Photoshop but definitely plenty enough.