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
A pretty big can. Widening it will cause far more problems than it’s worth. Why do you want to have a 20px margin to the right of videos?