The CommandBar at the top uses a transparent image. The green blue gradient under it is controlled in the shellstyle.dll > UIFILE on Line 525 (default shellstyle. Else search for FolderBand)
<TemplateBackground background="Gradient(argb(255, 4, 80, 130), argb(255, 17, 101, 132), argb(255, 29, 121, 134), 3)" />
The image that overlays it is located at
Explorer & Shell > Explorer > CommandModule > <1>The details pane gradient is located in shellstyle.dll > UIFILE. Search for *layoutstyle (where * is: documents, games, generic, music, and/or photo.) In the <TemplateBackground background= line change the gradient.
Alternatively you can use the attached shellstyle.dll below. It's from an old theme of mine. The UIFILE was modified by Michael over at AeroXP to allow images to be shown in the DetailsPane.
Image list:
200 - Generic files command bar image. (Replaces the gradient.)
300 - Generic files details pane image.
400 - Music files details pane image.
401 - Music files command bar image.
600 - Photos/Videos files details pane image.
601 - Photos/Videos files command bar image.
700 - Documents files details pane image.
701 - Documents files command bar image.
800 - Games details pane image. **
** CommandBar image for the Games explorer was never achieved. It uses the generic files command bar image (200).
Shellstyle:
http://longhornfusion.net/shellstyle.zip