By default Windows 10 will show thumbnails instead of application icons when a shell extensions is registered that knows how to deal with that file type. In your case that is the Rhino shell extension doing that for you.
You can turn this off by going into
System settings, selecting
Advanced System Settings, then click the
Settings... button in the
I personally like to select
Adjust for best performance, and make sure that each and every checkbox is deselected, but in your case you just need to make sure you deselect
Show thumbnails instead of icons.
edit to turn of for a specific folder like the desktop you should open your Windows Explorer and browse to your desktop, then on the far right side you see a v-icon next to a question mark. Press the v-icon. From the opening ribbon menu select
Options. Go to the
View tab and select
Always show icons, never thumbnails.