Its safe to say that an easy way to pull a thumbnail is to snip a screenshot of the thumbnail in the content browser. The only issue is you have to edit the thumbnail and rotate it to the sky so only the gray background is showing. When you do this you cannot get the angle you want. If you have the pattern floor it is very hard to change the background color in a paint program and or be able to select just the object.
If you could either make it where you can turn off the floor and shadows or change the color to match the sky, the sky would be a huge time saver for a lot of people.
You can see the attached picture that merry-go-around with the floor would be hard to remove the background in a image processing software because of the shadows and checkered floor, but in the 2nd image you can see the gray which is easy to change the color with the paint bucket or use magic want to select and delete the background.
Thank you for reading this,
John