It would be possible to modify the theme headers (i.e. all of them) with a function-call to display custom header info *if it exists* in the db for that blog. Much like other options, etc.

In cases where people have not added anything, nothing will appear.

The advantage of doing it this way is that it does not have the overhead of giving everyone a means to edit themes. All it takes is a textbox a function & a db-entry.

True, but it would have to be called from the header.php page of the theme and at present access isn't allowed.

Unfortunately it uses some specific CSS code that is essential to the point of the post.

I've read comments requesting wordpress.com to allow people to edit the CSS of themes - which would be complicated as each user would end up with their own twiddled versions of the theme files.

However, if you find a method of inserting header information & make that customisable you could achieve much the same effect:

* CSS can be overruled (if customised after theme CSS)
* CSS can be called in from remote source

Useful and doesn't require theme-editing.

Thoughts?