Catching Elephant is a theme for Tumblr.
Please look through all the answers here before asking a question. The same questions keep coming up. A lot of customisation can be done with custom css. Try googling css background for example.Catching Elephant is a theme by Andy Taylor
That’s how it works now if you post a large image. Although you need to click the magnifying glass that comes up over the photo. Clicking anywhere else on the photo will still respect the click through link.