dropbox-photo-frame | digital photo frame that uses Dropbox

First, find your DropBox access token. You can the instructions to generate one here. Then, go to the following website and substitute YOURTOKEN with your own access token. You can optionally set the timeout in milliseconds as well. 10000 being 10 seconds. There is alos the option set a blackout period. It will just show a black website then, it will not really save any power.
The application is a small React app that generates a website in the build directory. When using a Raspberry Pi, you can use the following guide for setting up a fullscreen chromium webbrowser, aka kiosk mode. Clone the repo and run either npm install or yarn to install the dependencies. Edit the file src/config.js to add your DropBox access token. You can the instructions to generate one here. In the config you can also set the timeout in miliseconds and the path to the directory of your pictures. Then run npm build or yarn build to transpile the code to the build directory. For my Raspberry Pi zero w I installed Apache2 and symlinked the build directory to /var/www/html. This project was bootstrapped with Create React App.