Gmail Themes
Following the footsteps of Google’s personalized homepage, Gmail added themes. Once the new option is enabled in your account (as usually, Gmail’s new features are slowly rolled out), you’ll find a tab named “Themes” in the settings page and you’ll be able to choose from 30 themes. “We wanted to go beyond simple color customization, so out of the 30 odd themes we’re launching today, there’s a shiny theme with chrome styling, another one that turns your inbox into a retro notepad, nature themes that change scenery over time, weather driven themes that can rain on your mailbox, and fun characters to keep you in good company,” mentions Gmail’s blog.
Gmail’s help center provides an interesting tidbit about the new themes: “In some cases, you can also customize by location. Some themes change during the day, and we use the location information you provide to correctly time these changes with your local sunrise, sunset, and/or weather. If you select one of these themes, you’ll see a Country/Region drop-down menu appear.” Source: http://googlesystem.blogspot.com/2008/11/gmail-themes.html