clipped from: www.flickr.com Privacy Uploading by Email
With our upload system, you can add a little bit of text (the pink bits below) to your Flickr email address (the green bits below) to set privacy levels as you upload. These permissions will override the default upload permissions you set here.
Let's say your magic email address is foo13bar@photos.flickr.com. Then you could use:
foo13bar+friends@photos.flickr.com - Visible to friends
foo13bar+family@photos.flickr.com - Visible to family
foo13bar+ff@photos.flickr.com - Visible to friends and family
foo13bar+private@photos.flickr.com - Only visible to you
foo13bar+public@photos.flickr.com - Visible to everyone
Tip: Save the addresses you use frequently to your address book so you can email on the fly.