WebClap.com is a Japanese site that offers a special download that you can add to your website. Basically it’s a feature that a user can click showing they like the site, then allows them to enter text. You can then analyze how many many claps you get when and what they liked about the site. The idea was to replace having to put up your email or adding a forum for such. Perfect for a blog, illustration, or personal graphic site. Many anime illustration and 4 panel manga sites use it.
You can also customize the page that they thank you on. There you would likely have an image telling them thanks. There’s a free and paid version, the paid giving a tiny bit more freedom. Other features include email forwarding, IP tracking, and word filtering in where the message is rejected. You can also have Web clap created and hosted by Webclap.com with the parent site SimpleCGI.