Image Gallery feature photo album bsv works if your image is in database. As soon as I put small image and enlarged images in file folder the image gallery picture click give document not found error. I tried setting it with different properties but image gallery feature not working when images are in file folder.
Make sure you have a rule which defines the file path of the storage in FilePathAttribute... it should be initialized.
Else share the Logs over here when you create the object or do edit.