The LinkGalleryFiles method links specific Raw files to specific photos in a gallery. This method is new in API 1.8.
void LinkGalleryFiles( long fileIds, long photoIds )
The arrays provided in the fileIds and photoIds parameters should be of the same length. Each element of the fileIds array identifies a gallery file to be linked and the element of the photoIds array in the same position identifies the photo the file should be linked to. To remove a link, specify zero in the corresponding position of the photoIds array.
All file and photo identifiers must refer to files and photos in the same gallery.