How to change the Sharepoint theme template option

C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS\1033

 

have one file name SPTHEMES.XML , this is the file control the theme for SharePoint. if you want to add some custom theme make sure here is added

 

1033 is for English version , 1031 is German…if you have more so different language keep at different folder .