While working on my map, I've found it annoying having the same Notepad++ icon on all the different filetypes.
So I made some of my own - the same logo with different colours, like so:

FileTypesMan download: http://www.nirsoft.net/utils/file_types_manager.html

If you want them, I've uploaded my icons here: https://www.mediafire.com/?ytz8zwdkk9gw6wy

If you want to make your own logo, you can download a plugin for Adobe Photoshop that allows you to edit and save in .ico format. Link: http://www.telegraphics.com.au/sw/product/ICOFormat (DL links are in the bottom right) Obviously you'll need to download 32/64 bit depending on your version of Photoshop. To install the plugin, simply move the file to <Photoshop root folder>\Plug-ins\File Formats, then restart Photoshop.

I believe there is an equivalent plugin for Paint.NET too, but I haven't tried it.

To use FileTypesMan:
Open the .exe, scroll to the filetype extension you want to change the icon of. Double click, then click the "..." next to Default Icon. Browse to the .ico you are using. Click OK. Then go to File>Refresh Desktop. Done!

Here's an example of mine:



You can obviously use this tool for other filetypes as well, and it has more uses than just icons!

I don't use NP++ but thanks for the plugin and tool will come in handy