For Windows PC format is easy but is cumbersome,
But if you have to be doing for MAC which is my case, copy the MAC changes the format for the new icon to the right size, etc.
Linux and to take the appropriate size.
All I'm saying is that when exporting to Node-WebKit you can choose the icon you will have the game, instead of the default icon that comes with Construct 2
It would be an added value software Construct 2