CocoaDev

To get a generic folder icon you have to use the NSWorkSpace API as follows:

        NSString *folderFileType = NSFileTypeForHFSTypeCode(kGenericFolderIcon);
        icon = [[NSWorkspace sharedWorkspace] iconForFileType:folderFileType];

You can generate other system wide icons by using the following HFS type codes:

• kGenericFolderIcon
• kDropFolderIcon
• kMountedFolderIcon
• kOpenFolderIcon
• kOwnedFolderIcon
• kPrivateFolderIcon
• kSharedFolderIcon