Did you know that each social media site has different sized and shaped profile and cover images? To make the most of your branding you need to maximise the space you have, this link has the main sites listed and the sizes of the different spaces (including the place where the profile picture goes over a cover photo.
Here is an example of what I mean:
This is the Button Help Cover Photo for Facebook, the profile picture covers a small area at the bottom left, and the total size of the picture is 851pxl x 315pxl:
This is the Button Help Cover Photo for Google+, the profile picture covers the whole height of the cover photo, on the right side. While the total size of the picture is 890pxl x 180pxl, the actual size you have to work with is 614pxl x 180pxl.
As you can see from this example, you will get the best out of branding on social media by working with these different sizes, and creating different cover pictures for each kind of social media.