There are different kinds of photos you can post on your Page – the three most important ones are Profile Photos, Cover Photos and Timeline Photos.
Profile Photo. It’s the first thing users see when they encounter your Facebook Page. It should be well-fitted to your brand image and be of high quality. It shouldn’t be larger than 180×180 px, because then Facebook will make you cut it to those dimensions. Changing your profile picture will appear on your Timeline, as part of your activity.
Cover Photo. The cover photo appears at the top of your Page. It’s dimensions are 1200×445 px, so upload a photo that matches. If you don’t, Facebook will automatically make it fit, making it looking blurry. If you upload a photo with bigger dimensions, you can edit the image and select the part you want to be displayed. Changing your cover photo will appear on your Timeline.
Timeline Photo. Any photo that you upload normally through your Page’s timeline. It’s ideal dimensions are 940×788 px and they will appear in your fan’s News Feeds. If you want them to be associated with your Page, you should make them have something in common – a logo in the same location, similar colors, or a unique layout.