1. From the Site Actions Menu, Select View all Site Content
2. Select the Shared Resources Library
3. Check Out, and begin editing the CUSTOM.CSS file. (Note: the icon will change when the file is checked out.)
4. Modify the following classes accordingly to change the background image and or height.
5. When satisfied, check the CUSTOM.CSS file back in.

/* Header Container (The color border around the image) */
.header-container {
 background-color:#227ed2;
 }

/* Header Image (The image itself)  */
.header-image {
 background-image:url('headerBG100ox.jpg');
 background-repeat:no-repeat;
 background-color:#227ed2;
 color:#FFF;
 height:100px;
 /* border:1px dashed #FFF; */
 }

Tips:

• To remove the banner entirely, place DISPLAY:NONE; as the last property for both classes.
• We recommend saving any background images to the Shared Resources library.