A header image can be added to the top area of your blog. You can also upload multiple header images to be displayed as a slideshow.
Proceed to the Customize section of your blog’s cms and select Header Image from the list of options. From there you can upload up to 6 header images and edit the header area in a number of ways.
The header image display width is 960px and the height is flexible. If you upload multiple images we recommend keeping the height of all your header images the same.