I am working on a project which involves adding multiple layers hosted on ArcGIS Online such as land use, vegetation, terrestrial ecoregions, population, etc. I am using the Javascript API. I would like to add a Panoramio layer. Can this be done?
This project might be helpful ESRI_Panoramio_Web
The website links are dead but there is a Code Attachment that has a dojox.rpc.Service with an SMD file to connect to the Panoramio API. You may be able to use it out of the box or modify it to suit.
Otherwise the Panoramio API has some details on making requests using an extent. You could then convert the results into ESRI JS graphics.