How do I change my banner on my profile?

I was just watching a friend profile and I saw that his banner has changed from the normal one. And he is the only one of my friends that has it changed. I would like to know how he did that.

My banner:

His banner:

Your banners background image will change depending on what Summoners Icon you currently have.

For most Summoners Icons the banner will remain the same (yours) but in some cases it will change to something else. Currently there are 5 Icons that will change your banner:

• The 4 Spirit-Guard Udyr Icons
• The Pulsefire Ezreal Icon

As you can see those are only obtained by buying (or obtaining in general) an ultimate Skin.

Another thing that changes the appearance of the banner is you rating from the last season. You will receive a border if you were Ranked Silver or above at the end of season 4. The border is going to be in the color of your highest division (3v3, 5v5 Solo, 5v5 Team count) at the time the "end-of-season-rewards" are rewarded.