The ideal size for uploading a Cover photo to Facebook is 851 pixels wide by 315 pixels tall. If you upload cover photo that is smaller than 851 pixels wide by 315 pixels tall, the image will get stretched to these dimentions losing quality and appearing blurry.
The image uploaded as a profile picture needs to be 180 pixels wide by 180 pixels tall or larger, Facebook will shrink the picture to 160 x 160 pixels with a 5 pixel white border surrounding the image
Photos uploaded to your timeline are automaticly sized to 403 pixels by 403 pixels, images larger than this are automaticly sized down for this reason we recommened uploading images at 806 pixels by 806 pixels.
Images smaller than 403 pixels by 403 pixels are streached to fit. Larger images are shown on the timeline at 403 pixels by 403 pixels. They are shown centered which may mean a message may be lost by been cut off.
Timeline Photo Hilighted
If you wish to highlight an image on your timeline upload it at 843 pixels by 403 pixels otherwise the image will be resized and will not display as uploaded.