I suppose the script hasn't this feature.
Is possible when anybody visit the website, he can choose his favorites thumbnails and put it in a "fauvorites" folder created for this specific purpose. When anybody visit again the web, each one ever will have the folder with his fauvorites thumbnails into. It could change the state of a thumbnail (favorite or no) with ctrl+click over the thumbail.
Is this posible? Is it easy? In a future?
Sorry for my english.