If you use the configuration, that you pasted, with the default content provider of the RadFileExplorer
control, you will get these error message: "Failed to map the path '/img/photos'
". In order to avoid any unexpected behaviors you need to use root-related paths :
"*.jpg, *.gif, *.png, *.txt, *.bmp"
In case, however, that you use a custom provider, please open a new support ticket and send me your project. I will check it and do my best to help.
the Telerik team