After signing up for an Imgur account so I could embed some pictures in a Fargo post, I've just discovered that you can insert media into Fargo.
Choosing 'Settings>CMS>Check the 'watched folder' create a Watched folder in your Dropbox account. Drag any media in there, wait for a few seconds and Fargo will give you a link to the media. It also moves the file into the Fargo>Media folder and organises it into a folder structure with year and month.
Here's an example.
The next step will be to see if there's a way to get images hosted in this way embedded directly into a Fargo post.