How can I mark files with badges in Windows?
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 :)
You can try something like UserInfoTip:
Select some files or folders, assign icons for them, and add a description to be displayed in Explorer's popup windows.
You can easily notice the marked files among other files and recognize their types by the icons.
Of course, nothing prevents you from creating an Icon Overlay Handler of your own. You can get started by using TortoiseSVN's code, but remember that there's a 15 overlay limit (which will get exhausted in no time if multiple programs attempt to set overlays), and icon overlays are not even recommended by people such as Raymond Chen.