The background image, logo, and room photos required size is a maximum of 1.5 MB. We also recommend having these images in a .png file type.
To upload the background image > Setting > Booking Engine Customization > Booking Page Editor
To upload the room images > setting > Booking Engine Customization > Booking Button Editor > Customize > click on the ‘edit room’ button
Here is the example booking page of one of our user: