Created attachment 4851 
expand icons

I propose to adjust the width between icons automatically, if at least one row already reached the window border. So the width between icons would depend on the window width. If you resize the window, the width between icons will change, too.

It would look tidier and it would blank unused space, but fill the whole window.

I attached a screenshot for better understanding.

Btw this ability is implemented in the Windows Explorer.