Thumbnails created by a namespace extension that do not receive decorations (e.g. shadow)

Question

I wrote a namespace extension to represent the remote file system. IExtractImage is implemented to provide images for various sketches supported by the shell. All this works correctly. However, I notice that the thumbnails that I generate when displayed in the shell view do not have any thumbnail decorations on them.

According to the MSDN documentation for sketch handlers :

Decorations, such as eye shadow, apply to sketches based on a user-selected theme. Decorations are provided by Windows; do not create them yourself. Windows can change the appearance of individual jewelry at any time, so if you granted you your rights, you risk losing synchronization with the system. Your thumbnails can lead to obsolescence or inappropriate.

Thus, it seems that the shell should beautify the image returned by my namespace extension with the appropriate eye candy (usually a shadow). However, no matter what I try, the images displayed in the shell view are exactly the image I am returning from my interface. To cover all the bases, I even tried to access the local IThumbnailProvider element and get its thumbnail. The reverse image was also not decorated.

Is there any other interface that I might need for it to work correctly? What am I missing?

Thanks.