Ann, here is the link where Dave explained how someone can propose an image in a thread to be added to the database.
http://garden.org/thread/view_...
You can request Dave to 'lock' out your images from this option if you wish.
You can delete your images as well. Just go to the image in the database and scroll to the bottom and click on "Delete this image" and away it goes.
Personally, I am flattered should someone come across an older thread and find a photo not in the database & propose them to be added.
We are finding older threads and many folks that no longer post and since they publicly shared their images here to begin with, it would be a shame not to also include them in the database, IMHO.