Tweetbot for iPhone has been updated today to add Twitter's new profile image headers. These header images look close to those on Netbot, but on Tweetbot they look larger. you can't upload these images from Tweetbot, it only displays them.
The update also brings the ability to create custom locations using the app's geolocation features. also included are various other fixes and improvements.
Tweetbot for iPhone is available for $2.99 in the App Store [iTunes Link].