With Facebook’s Timeline, you’re no longer limited to a single thumbnail as your profile image. You can post a massive Cover Photo (850 x 315 pixels, or 8.5 x 3.2 inches).
To change your Cover Photo, move your cursor over the cover canvas. Click the Change Cover box and select Choose From Photos if you want to post a picture already on Facebook, or Upload Photo if you want to add a picture from your hard drive. Once you pick your photo, click Save Changes.