Firstly, if you are in the USA or UK, this is my web site, the look and feel is finished but I have been too busy to create much text content.
https://compuaidusa.com
I circumvented the need to pass a class in a link by using several different plugins:
1. https://www.ads-software.com/plugins/show-content-only/
(the above plugin allows you to display only the content of a post and using “page links to”, I am able to set the link to set the dimensions of the lightbox / thickbox I am using. Try my menu items on the site)
2. https://www.ads-software.com/plugins/masonry-post-gallery/
(I use this to create the tiles on the main page, this plugin actually allows me to set a class of “thickbox” for it’s links, I don’t think this will help you”
3. https://www.ads-software.com/plugins/auto-thickbox-plus/
(I use this to display content when you click on the tiles)
I really had to rummage my brain to remember how I set this up. If you have questions, I will try to help.