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Twitter now has an option to create your own header. When you go to your profile account you can now select to not only edit your photo, but also your new header.
After selecting edit another screen will give you more options, one will be to change your header. 
The new cover measurements are 1252×626, to create using My Memories software you would open a new album and select design your own page
Select Landscape, and custom size 1252 by 626
once you have selected your size, you can add any designs you wish. You can even resize any page you have already created to create the new header. Then you will save the new creation, and upload in the new Twitter header section by selecting Choose existing image from your computer.
Here are a couple I have created using Touched by a Butterflies Day at the Spa Kit.
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