I am using Google Apps free version. In the Gmail, I don't have themes. How can I use themes?

I followed the following address

https://mail.google.com/a/yourdomain.com/#settings/themes

as seen in this link but no luck.

Am I out of themes, because I am a free user?

ADDED

I do not see the "Themes" in the "Mail Settings". I have checked with two Google Apps domain; both do not have Themes. Am I the only one? How may I complain?