Insert a blank space or rule in the 'extra fields' section
I'd like to suggest the ability to insert a blank space or rule (that follows a person's CSS) in the 'extra fields' section.
One field after another gets a bit boring and for some may be a bit difficult to read. Having the ability to 'insert a space' instead of 'insert an extra field' would give people the ability to break up and show their extra fields into different categories or sub sections.
This could be developed a bit further and you could insert some text that would appear as a sub-heading or even the ability to insert a graphic file.