Notational Velocity is a note-taking application, not a file/image organization tool.
Notational Velocity allows you to organize your notes by search, through the combination of searching and creating. The goal of NV is to avoid the need for explicit categorization.
See Issue 22
See Issue 27
See Issue 8
See Issue 6
First, know that you can set a global hot-key to bring NV to the front under Preferences > General > Activate NV Shortcut, provided that the app is already running. If this is still unsatisfactory, then see Issue 33.
See Issue 87