It depends on where you want to store the files; you could just copy the configuration section from :development if you want to place uploaded files on your droplet, our LocomotiveCMS solution do just that and it works fine, however it wouldn't scale very well i.e. if you want multiple web servers to have access to uploaded files.
If you are using MongoDB with Carrierwave for Mongoid, then you could store your files in the database using the GridFS, however I don't have any experience with this myself. You can read more about it on Carrierwave Mongoid's GitHub page.