Adding a Custom Header Image
To add a custom header image, you’ll need to navigate to the Appearance tab in the Tumblr Dashboard, which is located in the “Customize” sub-section.
Once inside the Appearance tab, you’ll need to scroll down a bit and look for the “Header image” label. By default the Headline theme does not contain a header image. It uses your blog’s title as a header. To add a header image, click “Upload” and select your custom graphic.
Please note that the maximum width of the theme is 870 pixels. If your custom header image is wider than 870 pixels, it will run beyond the third column and not look very good. For images less than 870 pixels wide, the image is centered.
For you CSS-savvy users, please note that a top and bottom margin of 1.5em is added to the #header-image element. If you’d like to flush your image to the top of the page and left-justify it, you’ll need to override the defaults using the following custom CSS:
#header-image { margin-top:0; }
#header {text-align:left; }