Random File Picker can quickly choose and open random files from a set of directories. Files can be filtered so you can for example look only for images.
The directories that you supply to RFP will be scanned for sub-directories (first a directory is chosen, then a file from it).
In short it is a tool that makes decisions in your place. Not sure what wallpaper to choose for today? Let it decide for you. Not sure what movie to watch? It can open a random one in just a few clicks.