If you’re having problems changing the header image, do either of the following:
Manual editing:

Apologies if you guys are still having a hard time uploading the header. It should have been sorted out by now, I have no idea why it won’t work :-(
Custom CSS
Some people prefer not to have a header. To remove the header without touching the HTML, paste this in the Custom CSS box (it should be at the bottom part of the left sidebar when you customize):
#header { display: none; }
There is no option for a transparent background when you pick colors, however, you can do that by adding another bit of CSS.
/** For Header background **/
#banner { background: transparent; }/** For Navigation background **/
ul#navlist { background: transparent; }/**Removing Navigation link background on hover**/
ul#navlist li a:hover { background: transparent; }
If you have other options in mind that you would like me to add, please feel free to comment on this post!
Another thing to keep in mind:
If you decide to edit your HTML (without any knowledge of what you’re doing) and you end up ruining your layout, just use Tumblr’s Theme Recovery Tool. It backs up the 20 most recent changes you’ve done to your theme. I hope that helps!
Go to http://embedagram.com and authorize the app.
From there, you don’t need to copy any codes, I’ve included it in the theme already.
This theme is also mobile-responsive! Be sure to check out how it looks on your tablets and smartphones :-)