When uploading an image to Online Sales Pro within our Quick Editor, we do zero cropping of background images. All that happens is we resize the image for server space. Since there are so many screen sizes and devices nowadays, browsers use algorithms to make them fit nicely for us. This means that a background image should never have text or specific images; it should just be a "background" in the literal sense.
Note: There are some sites and companies that use special custom code for certain background images, but we make tools for mass page creation.