The current k2 Image Gallery feature requires the user to zip their images and then upload. This is not very efficient because the client has to keep a catalog of folders with the images for each K2 Item. If the client wants to change or add to the image gallery then they need to zip a new set of images and re-upload to that K2 Item.
I think the Flickr integration in the K2 Image Gallery is a better method. Once the Flickr set URL is pasted into the K2 Item Image Gallery, then the client can change the set of images on flickr. The client no longer needs to keep a catalog of images on a computer. The client or business can give access to the flickr account for others to change the images that will display in the K2 Image Gallery.
If you or your client uses a Macintosh then they have the photo organizing and editing software called iPhoto. iPhoto now can share to Flickr. These means that a client can edit images, change the order, add and subtract images from an album in iPhoto. Once that iPhoto album is shared with a specific Flickr set then any changes in iPhoto will be synced to flickr automatically and therefore the k2 Image gallery will be updated.