What about big icon on the shell dash? It size also can be modified to match with your application icon. To modified icon size on the dash, we need to modified dash.js file which write in Java. So, follow this step,
2. Search for 'iconSizes' as you see on the screenshot. In this screenshot we can see it icon maximum size is 64. So an icon on the dash will be show in 64 size.
3. To make small size icon, just delete the bigger value. For example on this screenshot, I delete 64 and 48. So an icon on the 'dash' will be show in 32 size.
5. Re login. Now you can see the icon is small in 32 size.