In the UpMenu administration panel, as a customer using online ordering systems, you have the option of uploading your own background to the iframe.
Uploading background to iframe
Go to "Website" select "Theme".
Expand the options, select "Code Editor".
Go to "Assets" and upload your own photo file for the new background. We recommend photos with a width: 2000px, aspect ratio: panorama, format: jpg
In the "Styles" section open the custom-style.css file and add to the first line below code:
You need to change part "FILE_NAME" and enter the name of the file you want to upload from your computer. The file extension entered in the code must be the same as the extension of the uploaded file in Assets.
5. Select "Save".
6. The background you uploaded is now visible on your restaurant website.