Finally, if you simply cannot find a theme that you like or wish to use a custom background such as your company's logo, you can make your own stationery for Outlook 2010.
Open a new email message. Apply fonts, bullets and other effects to the message. You can insert shapes, clipart or any other object you choose.
If you want to use a color for your stationery background, you can do so by going to the Options tab, clicking Page Color in the Themes group and selecting a color.

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If you want to add an image as the background, go to the Options tab and click on Page Color. Click Fill Effects at the bottom of the drop down. Go to the Picture tab. Click Select Picture, navigate to the picture you want to use as your stationery background and click Insert.
Once you have designed the custom stationery theme you want, go to the File tab of the message window and select Save As. Enter a name for your custom stationery. Select HTML in the Save As Type list.

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Click inside of the address bar at the top of the Save As window, type (or copy and paste) %appdata%\microsoft\stationery and press Enter. When the Outlook Stationery folder opens, click Save to save your new, custom stationery. Close the message you used to create the theme.
The next time you open the Theme or Stationery window, your custom theme will appear.
Please note that the standalone version of Outlook 2010 does not include themes. You must have Word installed as well in order to use them.