Tapbots has just updated TweetBot for Mac to version 1.3 adding some neat new features that made it to the iOS version a while back. The biggest feature is the new media timeline which turns any timeline into a photo and video one only, you can view this by clicking the button next to the search box. You'll also now be able to see cover images on user profiles, and double clicking the titlebar above a profile view will scroll the profile back to the top, double clicking again will scroll their timeline/mentions/faves to the top.
Tapbots has also fixed issues with unread items obscuring notification/error messages/attached post windows, and fixed an issue where text was still editable after being tweeted.
You can get the update over on the Mac App Store.