A co-worker and I were just discussing how to upload a bunch of photos to Flickr, but only make them viewable by our client so they can start selecting favorites for an ad.
You can make any Set of photos and or any single Flickr photo private. That makes the photos in that Set only viewable by you. First step complete.
Flickr has a feature called Guest Pass. This feature generates a URL that bypasses the privacy of that item. Give this URL out to anyone you would like to see that item, even though it’s marked private.
Easy. We now upload photos to a private Flickr Set, and give a Guest Pass to our client so they can begin making selects.