Thumbnail wizards, how do I make a great avatar thumbnail?

So far, I've gathered these considerations:

Avatar thumbnails have these dimensions (if they are the same ingame and on the website):
>500*375px (old avatars)
>667*500px (current avatars)
Watermarks with your name are super gay and distracting.
The preview camera when uploading doesn't match what you actually see ingame, because it uploads a bit wider than the camera. (Maybe fixed by now?)
Also, ingame there's a frame around the thumbnail and part of the thumbnail is obscured by the text with its dark background. (I wonder how high the background is vertically in pixels, and where it starts and ends?)
Striking a pose makes it easily look more unique.
You can use a background to give context or highlight certain aspects.
Or, you could just render a scene in Blender and put the render in front of the upload camera to have more control.
Actually fiddling with the Unity lighting makes it look pretty.
It might be useful to have Unity scenes set up just for quickly making thumbnails.
Maybe have a "thumbnail studio" set up at the origin of the Unity scene, so you can skip fiddling with the thumbnail camera every time? (Or, just paste camera components into the preview camera.)
I remember there being some scripts for more control of the tumbnail, but I forgot the names.

Is there a tool to preview your thumbnail as it shows ingame in the menu? (As opposed to just seeing how it looks in Unity.)