Normally, here is what you see when you are entering App Switch in Windows 10 by pressing Alt + Tab with many apps running. Not a big deal, but it could be cleaner.
Here are some registry tweaks that you can use to make it happen.
Before we get started, let’s make a new registry key called MultitaskingView and a subkey named AltTabViewHost below that in the following location.
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\
To hide all open windows while in Alt + Tab mode, create a new DWORD-32 Value in AltTabViewHost key and name it Wallpaper, and set its value to 1.

You can also make the Alt + Tab app switch background transparent. Create a new DWORD-32 Value and name it Grid_backgroundPercent, then set its value accordingly, from 0 for fully transparent to 100 for complete opaque.


You can even dim the desktop so the Alt+Tab dialog can stand out even more. Create a new DWORD-32 Value and name it BackgroundDimmingLayer_percent, and set its value accordingly. Giving it a 40% will make it look like this:

That’s about it. Thanks to Winhelponline for discovering all these registry hacks.