When you feature a property, the system shows the photos in the order that the estate agent has uploaded them. 

To choose the photos you would like to show, you would need to have chosen to make your property a Premium Listing. To show the photos of your property in a different order without choosing a Premium Listing, we recommend you ask your estate agent to swap the order of the photographs. 

Please note that this may possibly affect the agents own website as well as the other portals.