Themes in a nutshell (Simplest Example)

Ok...

1. Go to your THEMES Folder on your Sharepoint site

   Mine is here
   C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\THEMES

2. Copy one of the Precanned THEME Directories (I used GRANITE) and Rename it to MYTHEME (Or whatever you want it to be)
3. Open your new MYTHEME Directory and sort the contents by type.
4. Delete all the gif files.
5. Rename the INF file (GRANITE.INF) to MYTHEME.INF
6. Open MYTHEME.INF
7. Replace the old theme name (Granite) with your new theme name (MYTHEME)
   It will look something like this
   

   [info]
   title=MYTHEME
   codepage=65001
   version=3.00
   format=3.00
   readonly=true
   refcount=0
   
   [titles]
   1031=MYTHEME
   ... Shortened to save room.
   1054=MYTHEME
   

8. Save and close it.
9. Open theme.css and delete its contents.
10. Then add this css code
    
    

    .ms-bannerframe,.mrGRHeaderBackGround, .ms-storMeFree
    {
      background-image:url("logo.gif");
      background-repeat:no-repeat;
      height:89px;
      background-color:#FFFFFF;
    }
    

11. Save and close it.
12. Open Paint and make a file called logo.gif and save it in your MYTHEME directory.
13. Find and open the SPTHEMES.XML file
    

    Mine is here.
    C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS\1033

14. You will see a bunch of <Templates> tags.
15. Copy and paste one of them and edit it to look like this
    

    <Templates>
     <TemplateID>MYTHEME</TemplateID>
     <DisplayName>My Theme</DisplayName>
     <Description>Theme created specifically for ME</Description>
     <Thumbnail>images/thnone.gif</Thumbnail>
     <Preview>images/thnone.gif</Preview>
    </Templates>
    

    The image THNONE.GIF is found in the C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\IMAGES directory. If you want a different image for your thumbnail you just need to put it in the same directory as THNONE.GIF and reference it in SPTHEMES.XML.
    
    
16. Save and close it.
17. Once you are done you just need to go to your Sharepoint Site Settings -> Site Themes and select "My Theme" from the list.
18. Your site will get your new logo at the top.