XYplorer Beta Club
I found this feature from IdImager called Travel Mode.
The idea of Travel Mode is you can still view the pictures even when they are not currently on the computer.
http://www.idimager.com/WP/?page_id=20
With Photo Supreme you have previews of your images stored inside the catalog. So even if your images are physically located on your network or external drive, they travel with you. The size of your previews is configurable. If you are in “Travel” mode, Photo Supreme remains fully functional. You can even access your images as you are enjoying your Cuba Libre on the beach. Back home you switch off Travel Model and push the changes back to your image files.