to get the html you did provide in comment:
<%= link_to image_path('webprojects/BIG_IMAGE.PNG'), title: "tITLE O THE IMAGE", data: { caption: "<strong>Lorem ipsum dolor</strong> sit amet, consetetur sadipscing"} do %>
<%= image_tag 'media/thumbnails/THUMBNAIL.PNG', alt: 'Alt Image Text' %>
<% end %>
Notice you should put your pictures in the assets folder to get it working.