File Roulette is an app developed by former Geckoboarder Daniel Upton that generates a URL that returns a different file in your Dropbox each time you visit it – either randomly or in sequence. This tool can be used to create an image widget that displays a new image after every refresh, which occurs automatically every hour.
Add a new Image widget from your dashboard.
Open file-roulette.com in a new browser tab or window.
Click Log in With Dropbox.
Dropbox will ask you to allow File Roulette access to a folder. This will create a File Roulette folder within the existing Apps folder in Dropbox.
Then, you'll be presented with 2 URLs: one for random order and the other for one-after-another (Round Robin) order. Copy one of these to your clipboard.
In Geckoboard, paste the link into the URL field.
Then click Save.