Well...
It is very easy to have custom ICON for your files. Just you need to register the file type.
.NET Installer setup have this facility and it works great.
Another thing, if you want to use Double click to open your application for that particular file you can also do this easily.
Just you need to change some registry keys and you are done.
See how I did that in my application :
Folder protection for windows using C# & Concepts on Windows Shell menu for Folders[
^]
I hope this will help you.
Cheers. :cool: