For those of you finding your images truncated by the square requirement for images here, I recommend a free program called Xn Convert: https://www.xnview.com/en/xnconvert/. My website (Shopify) requires square images, so I use this all the time.
Xn Convert allows you to batch resize your images AND the canvas size at the same time, so that you can fill in any area around your image with the background color of your choice in about three seconds. I resize my images to be 1024 pixels on the longest side, and resize my canvas to 1024 x 1024 pixels, setting the background color to white. (Note, ALWAYS resize down, never up -- if your images are smaller than 1024 pixels already, then you need to start smaller. Keep in mind, however, that image quality can suffer if you go too small.)
Hope this helps!