Best size for overview and episode pictures?

What is the best episode picture size for my WDTV Live Streaming (Gen3)?

I would like to have a season picture for every single episode from my favorite TV-Show.

Therefore I save a “tvshowname - s01e02 - episodename.jpg” at the same place as the “tvshowname - s01e02 - episodename.mkv”. At the same place I save a folder.jpg with a picture of this season for the overview.

This works technically, but the pictures looks very ugly.

Somewhere I read the information, that every *.jpg should be fine, but the aspect ratio should be 4:3.

Is this still true for the WDTV Live Streaming (Gen3)?

What about other voices that says, picture must be 400 pixels (height) by 300 pixels (width) or 120x180 with 100dpi?

And should I create a folder.jpg with different size as the episode pictures?

Can someone please tell me the “best” size for all the desired pictures?

Hi, why not try both and see what results you get.