Increase Taskbar Thumbnail Preview size in Windows

Open Regedit & navigate to the following location: In the right-hand panel, create a DWORD value named MinThumbSizePx. Right-click MinThumbSizePx and select Modify. Set its decimal value to say, 300. Exit the Registry Editor & Logoff  > Logon.

You will now see that the taskbar thumbnail size has increased. Hope this helps.

How to make Taskbar Thumbnail Previews appear faster in WindowsEnable or Disable Thumbnail Previews in Windows File Explorer.