Question: Is there a way or a program that marks the icon of a file with a badge, similar to how Dropbox marks synced files with a green checkmark, and files that are currently syncing blue?

I'd use that to mark videos I've watched in a series.

Answer: 
I couldn't find a better solution, so I've created an open-source project for that. Available at <https://github.com/csomakk/IWatchSeriez>
Its nothing special yet, but it does the trick, and I'll try to work more on it. I Watch Seriez, IWatchSeriez :)

![enter image description here](https://i.stack.imgur.com/CmmqI.png)
You can use Rating in Windows Explorer as work around. Mark \* as read.

From File's Properties, it allows me to do file Rating from (zero star ~ 5 stars). Since I'm not using the rating feature to really rate a file, instead I use it for the purpose of marking it as a read file, no matter what file type it was. I also can sort out those read vs. unread files if I want.