In the following articles by Diane Urban, she lays out the basics of how to update your Twitter profile using Twitters new improved profile layout. The instructions include what the sizes of the images you’ll need and how to upload them. The following are the basic sizes you’ll need:
First, if you look at the sample profile image below, you’ll see that the new layout is very similar to the Facebook timeline header area. However, Twitter’s main profile image is about twice as wide and you need to understand where the safe area is so your text will show properly on all devices.
Your header image must be 1500px by 500px as it needs to spread out to fill large monitors. However, only a portion will be safely shown on all size monitors and devices.
If you are going to add text to your main image, you should leave 315px on each side and 60px at the top as these areas will be cropped off on smaller screens. The top 60px is where Twitters’ navigation bar goes over.
Your profile picture inset is uploaded at 400px by 400px. This will be resized as needed by Twitter.