Thank you Maru, and sorry for my previous unclear question:
I have a simple archiviz interior and a plane with the background image outside windows.
The material for background plane is a Corona Rayswitch material, I follow the Corona Helpdesk indications to make it.
I have no problem in render but I wonder to see the backgrond image also in viewport because it's easier and faster to adjust it (move and scale).
I hope to clarify enough, my english compete with my Corona skills..... ;-)
Thanks
Bye