File Roulette is an app developed by ex-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. We can use this tool to create an image widget that displays a new image after every refresh.
Add a new Image widget from your dashboard and give it a Title.
Open file-roulette.com in a new browser tab or window. Then, click Log in With Dropbox.
Dropbox will ask you to allow File Roulette access to a folder. This will create a "File Roulette" folder in the "Apps" folder in your Dropbox.
You should be presented with 2 URLs: one for random order, the other for one after another (Round Robin) order. Copy one of these to your clipboard.
Return to your Image widget config and Paste the URL path.
Select a Reload time.
Click Add widget to return to your dashboard.