Create Your Banner
You can actually insert any image into your Blogger header, but it will best serve you to edit a graphic so that it fits correctly as a banner. Otherwise, the image may be stretched and skewed, which can look amateurish and sloppy. In addition, by editing an image you can also add text with custom formatting and other modifications if desired.
Choose an editing program in which to create your Blogger banner. You can use anything from Photoshop to GIMP. Your best choice will be the program with which you are the most comfortable and familiar with. Start the application and insert an image you want to use for your banner background.
Since the banner is wider than it is tall, an image that is in landscape orientation will be a better fit. If you want to use a picture that is in portrait orientation, you can do so by inserting it into a long, narrow rectangular background. This is a beneficial option if you want to add custom text, such as a quote or phrase.
Add any text or special effects to the image that you choose. Once you have formatted your banner image so that it appears as you would like it to on your blog, adjust the size so that it is between 760 and 900 px wide and about 150 to 200 px high. Save the image and close the editing application.