While testing our app on the Kindle Fire Emulator I needed to verify my image processing was working correctly. By default the emulator has no images in the gallery.
Using Eclipse in the DDMS perspective click on emulator-544 in the Devices tab. In the File Explorer tab find the mnt directory and expand it. Find sdcard under than and then Pictures. You can use the "Push a file onto the device" button to copy image files into that directory.
You can also put them in the mnt\sdcard\DCIM directory or the mnt\sdcard\DCIM\Camera directory. The final directory might not exist but you can create it in the File Explorer.
At this point you will need to stop and restart the emulator. It does not appear to rerun the sdcard scanner while running looking for new files.
Make sure when you create the emulator that you enable "Keyboard support" in the hardware section of the AVD or you will have to click on individual letters to type anything which gets boring rather quickly. You can disable this is you need to test with the soft pop-up keyboard.