They’re simple but fiddly things!
We have developed two unique site themes for Sharepoint called MC (MyCheshire) and MCT (MyCheshireTeams) and we’ve possibly got another one on the way MCSearch (MyCheshireTeams Search).
Each theme needs its own .inf file and will require a reference in the SPTHEMES.XML file in this format. Usually, this can be found at C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS\1033\SPTHEMES.XML.
Add the following lines under tag:
Notice that preview and thumbnail paths are images/thghost.gif. By default, MOSS 2007 and WSS 3.0 will not have such image files. These will also need to be manually added to the images folder.
WARNING: Whenever deploying a change to an existing theme, after deploying the change and performing an iisreset on the desired server, the site theme has to be reapplied through Site Actions > Site Admin on EACH affected Site Collection.