This might be a photo of a popular menu item, album artwork or a picture of people using your product or in your office. Choose picture that your audience responds well to.
There is a note on Facebook about Facebook Fan pages Covers polices read it below.https://www.facebook.com/help/?faq=276329115767498
Cover images must be at least 399 pixels wide and may not contain:
1- Price or purchase information, such as “40% off” or “Download it at our website” 2- Contact information, such as web address, email, mailing address or other information intended for your Page’s About section 3- References to user interface elements, such as Like or Share, or any other Facebook site features 4- Calls to action, such as “Get it now” or “Tell your friends”
To get the best quality image and fastest load times for your Page, upload an sRGB JPG file that’s 851 pixels wide, 315 pixels tall and less than 100 kilobytes.
All cover images are public, which means anyone visiting your Page will be able to see the image you choose. Covers must not be false, deceptive or misleading, and must not infringe on third parties’ intellectual property. You may not encourage or incentivize people to upload your cover image to their personal timelines.