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
Don’t bother. You won’t even start to make any money until you have thousands of visits a day.
To put things (ads) between posts you use {block:Post[1-15]} {/block:Post[1-15]}. You can read about it here.