Bootstrap Question:

it's possible to add any kind of HTML content like headings, paragraphs, or buttons into thumbnails. Follow the steps below −

☛ Change the <a> tag that has a class of .thumbnail to a <div>.
☛ Inside of that <div>, you can add anything you need. As this is a <div>, we can use the default span-based naming convention for sizing.
☛ If you want to group multiple images, place them in an unordered list, and each list item will be floated to the left.