I painted the rectangle behind the tv to an appropriate size to match the 70 incher. I left it black, but actually noticed (and remembered) that it is not really black as much as it is charcoal. I'm finding that with the LED rope light shining on it it looks even more greyish (charcoal actually) and less black. And that seems to give the blacks on screen more "blackness". I'm liking it. I think I'm done with it other than adding a remote controlled switch I got coming from Amazon.
I could add MORE rope light for the lumens, but think this is good. If I turn off the LED (at night) the wall disappears into blackness. With the bias-light on, the rectangle is a visible charcoal black and the tv's blacks look blacker and contrast is slightly improved. You think the wall is black until you see black on the tv image. I'm liking that. Best is that the tv looks like it's floating in the air.
$13 for the LED rope light
$14 for the remote controlled switch
and whatever I have in zip ties and some clear tape.
What is the amp draw of the LED rope? Is it possible to have one of those powered by the USB port of the TV? On laptops at least those things routinely supply half an amp!