ES File Explorer is free off the play store. You can use this to look through the files on your SD card. As someone else suggested, move the pictures from the Bluetooth folder to the DCIM/camera folder.
To do so, do this:
Open ES File Explorer. It should open in the SD card partition. I know the Nexus 7 doesn't have an SD card, it just has an imaginary SD card.
Now go to the bluetooth folder. Hit menu, select all, copy. I use a different file explorer, but the options should be the same.
Go to the DCIM/camera folder and paste them there.
I say use the copy feature instead of the move or cut because I was moving pictures from one folder to another, the file explorer force closed, and then everything I was moving just disappeared in limbo somewhere. And if you used copy and paste, now you can go back and delete everything from the Bluetooth folder if they copied successfully.
Sent from my wireless telephonic device.