Twitter has recently changed the design of the Twitter profiles. You can now have a 
On a computer, you can keep the traditional background as well as your header, but on mobile devices, your profile will display your header when you use the Twitter app. 
It doesn’t seem to make any difference to the profiles displayed in HootSuite at the moment.
Worth having a look at though. You can find the Header in twitter.com by Edit Profile > Design
This is optional – you don’t need to update your header. What do you think – will you use it?