Have you ever wanted to set a custom icon instead of this generic 
icon for your extensions?
What you need is just a small jpg or png file. For my extensions I used 50x50 pixel icons. Be sure that you are not attaching your family picture which is a couple of mb.
1. Inside vizpacker navigate to bundle.js.
2. Find the row that contains icon and write your icon name like the one below ("./football.png")
3. Locate your icon file under the deployed extension folder in lumira installation. Note that bundle.js (now name is concatenated with extension name) and icon files are in same folder.
4. And the result!!!
Instead of modifying bundle.js inside vizpacker, it is also possible to modify the generated bundles file directly.
This file is stored under deployed extension folder that is seen on step 3.