Have you set your personal photo as a wallpaper in Windows 10, but aren't satisfied with its quality? You can increase it with a simple trick. 
When you set an image as your desktop background, the image is compressed to 85% and saved to a file named TranscodedWallpaper in your Themes (C:\Users\Iguru\AppData\Local\Microsoft\Windows\Themes). Sta Windows 10, you can override the default wallpaper compression for JPGs archives, using the registry. Let's see how:
1. At the same time, press the Win + R keys and in the run window that appears, write regedit and press OK.
2. Go to the following key HKEY_CURRENT_USER \ control Panel \ Desktop
3. Create a DWORD value that will be called JPEGImportQuality
4. Double-click JPEGImportQuality and set the value data to 100 based on decimal
5. Close the registry and restart it explorer (or your computer if you don't know how)
You will need to right-click on your personal image and set it as wallpaper again so that the TranscodedWallpaper in the following folder is replaced.
You will see that the size of the TranscodedWallpaper file has increased (as well as image quality) after setting JPEGImportQuality to 100. JPEGImportQuality can accept a decimal range from 60 to 100.
