Google has recently introduced Themes and now we can customize our look and feel of the email account. You can goto your settings tab from the top of your page and find themes, which is the last tab of settings page options.

Despite the availability of many desktop and Online email softwares, we find Gmail a much better experience for individuals as well as corporates. Specially with this new feature of themes it feels like you are checking emails in a space ship.
With this Gmail update, of giving user multiple design theme options to personalize user experience is a proof of future flexibility of the websites to adopt to the needs and likes of their users.
We have multiple reports of Firefox 3.0 crashing while using Gmail with graphical themes enabled. I am not sure what is wrong with it, on Google Chrome Gmail is running smooth.