Make taskbar icons' size bigger/smaller than options given Win 8.1
Solution 1:
You could try to change DPI Scaling Size
go to Control Panel -> Personalization -> Display
Method 1: uncheck the Let me choose one scaling level for all my displays and use the slider (smaller or gigger)
Method 2: check the Let me choose one scaling level for all my displays and select one option from the radio boxes (and you can also check the Custom sizing options)