You could tag the entire post as #stockphotos (like this post) which will put it in the correct category. Otherwise, make an effort to learn about Creative Commons and how licensing works. Just a made-up tag for permission is not recommended. Many people are using this "CC" followed by numbers and abbreviations for what things are permitted.
Once you choose a CC license, make it clear that your photos are licensed as such.
When the site is up and running, I will make sure this same choice is available and try to steer people towards licensing that permit you to make money from the use of your work.
All major image "sharing" and storing websites permit some form of licensing, although some places have been known to default to permissiveness that is only attractive to the website owners, not the artists.