Form Background Image Not Showing Correctly

I have set my form background image correctly but it displays a blank theme after publication. Kindly advise.

I checked your form and this is how it looks on my end:

Is this not the image that you used? Would you mind sharing to us what image did you try to use? Is it a custom image or one of the predefined images? If a custom one, please upload it in a file repository like Google Drive and share the download link here.

II have also cleared your form cache in hopes that it fixes the issue. Kindly try to completely clear your browser cache and test it again. If the issue persists, please share a screencast.

How-to-Clear-Your-Form-Cache

How-to-clear-web-storage-in-your-browser