You can customize the web interface of your Gmail account.
To customize the background of your Gmail account, click the gear icon in the upper right-hand corner and then click "Mail Settings".
Select the theme you would like.
To customize the view of your inbox, in Mail Settings, click "Labs".
You can enable any of the Labs listed to customize your Gmail account. Here are a couple we find most users like to enable:
- Preview Pane
- Default Text Styling