When you set up the booking system either for your Smoobu website or for an external site, you are requested to enter a Property photo. It is recommended to enter a squared photo, max 500 kb.
This photo will be displayed when your potential guest is searching for an accommodation within your site, as a preview of your property's photos:
If you need to resize your photos, read on: How can I reduce my photos without losing quality? (scroll to the last section)