I would like to suggest adding the ability to choose a header image from the media library in addition to being able to upload it from your computer (unless I missed it or it is not available with any of the various themes used on the blogs I manage -- both of which are quite possible). It would be a very convenient enhancement for the bloggers who have recurring events or just a one-off special event to be able the change the header to reflect it. An added benefit would be to be able to change it back without having to upload the same image again, which results in having one image listed multiple times in the library unnecessarily.
I don't have recurring events; I just like to switch my headers when the mood strikes. If I could do so without the hassle of having to go back to delete all the duplicate header images, I would love WordPress even more!