One suggestion, with respect to the use of the brass washers - you might want to consider using brass faucet seats ( seen on the left side of the picture), instead.
True, they are more expensive than washers... a little more expensive, given the skyrocketing price of brass at the hardware stores... but they are more visually appealing, and seem to fit perfectly with the function of implementing a pushbutton or framing a large LED ( such as Adafruit's new 8 mm neopixel devices, or other 10mm ultrabrights ).
Last I checked, you can buy packs of 25 at Lowes or Orchard for about $25, or a buck apiece.
@Max I was going to suggest you used one of the usual TV ratios of 4:3 or 16:9 but I think @perl_geek's comment
You might want to consder employing the Golden Ratio (1.618 : 1, close enough for government work) in your rectangular layout.
is spot on - old TVs were't wide enough and new ones (16:9) always look too wide to me. I did come across the Golden ratio, as the Golden rectangle, years ago and the Wikipedia artilde on it is good (if a little over my head maths-wise :-) :