Different sized image gallery?

I have some images coming in from a different website, so I don't have any control over the sizes of the images, they vary in width and height. And I need to create a good looking gallery out of these images. I have access to the thumbnails(created by that third-party website) and the original sized images. I will also need to add some text fetched from that website, like title of the image copyright text etc.

Currently I am using bootstrap columns where the width and the height of an image block is fixed via bootstrap and custom css and then I put the image in the middle of that block with text-align, but frankly it looks ugly.

I am look for a more pleasing looking gallery, and it needs to be responsive, what can I do ?