Is it possible to use multiple databases?

Yes, if using the Enterprise version.

Using Multiple Databases
Sometimes it can be useful to run multiple databases. An example being completely unrelated image collections. While doing this is currently a little awkward it is quite easy and takes just a couple minutes. To use multiple databases follow these three steps...

From the main menu, select Settings & Help | Application Settings, then go to the Advanced Configuration tab. On that screen key the name of the desired database in the Database Name edit box. If you expect the database to already exist, press the Test Connection button to verify access, then press OK, at which point DBGallery will restart and use the that database. If the goal is to create a new database, simply press OK after keying the database name and IGNORE warnings that says the database doesn't exist. Keep pressing OK until DBGallery is restarted, at which point the new database will be automatically created.