When browsing Reddit, click 'save' and any linked image will be saved to your Dropbox in the appropriate folder (Cars, EarthPorn, Cats, etc.) under '/Photos/SubRedditName'. If you want to just lump them all together, change the 'Dropbox folder path' to 'Photos/WhateverYouWantToNameTheFolder'.

This Trigger fires every time you save a post on reddit.

This Action will download a file at a given URL and add it to Dropbox at the path you specify. NOTE: 30 MB file size limit.

Put images from my 'saved' #Reddit's to a Photo album in #Dropbox.