Hey, One of my friend is using BB and according to him you should do this things to solve your problem,
1. In the media application, press the Menu key.
2. Click Explore.
3. Navigate to a folder that contains media files.
5. Press the Menu key.
6. Click Show Hidden.
Once the hidden pictures are shown, scroll to them and go into their properties and change the hidden value.
Hopefully you will find it helpful.