In the new release of ProjectWise Select Series 1 (Refresh update) - version 08.11.07.133, users can see document thumbnail in the document list window by enabling View=>Thumbnail. "Preview Pane" can be turned off to recover more screen space.
After document thumbnail has been extracted, users can see document thumbnails in ProjectWise Explorer client by enabling "Preview Pane". The "Preview Pane" is at the bottom of the screen, it does however occupy screen space.