In internet ho trovato questo articolo che descrive i passi necessari per installare un nuovo template su SharePoint:

Creating Themes in MOSS 2007  On the SharePoint server go to the Themes folder e.g. c:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\Themes Make a copy one of the existing theme folders and its contents rename it e.g. MyTheme. Rename the .INF file within the MyTheme folder to MyTheme.INF Edit MyTheme.INF. At the info section, Change the title, to MyTheme. Change codepage, e.g 22200. In the titles section, rename the names to your new name. this section is to present the name in the different language. Provide an image to give a preview of your theme. This image should be placed in C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\IMAGES. E.g. tmbMyTheme.gif Modify the c:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\Layouts\1033\SPTHEMES.xml to include a reference to the new MyTheme theme <Templates> <TemplateID>MyTheme</TemplateID> <DisplayName> MyTheme </DisplayName> <Description> MyTheme has a white background with blue control areas and orange highlights.</Description> <Thumbnail>images/tmbMyTheme.gif</Thumbnail> <Preview>images/ tmbMyTheme.gif</Preview> </Templates> Modify the CSS within MyTheme folder to personalize your theme. Run iisreset from the command prompt Apply the new theme to a “test site”,.