Use small icons, TaskbarSmallIcons

Use small icons:

reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v TaskbarSmallIcons /t reg_dword /d 1 /f

Do not use small icons (default):

reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v TaskbarSmallIcons /t reg_dword /d 0 /f