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 :-) :
Replay available now: A handful of emerging network technologies are competing to be the preferred wide-area connection for the Internet of Things. All claim lower costs and power use than cellular but none have wide deployment yet. Listen in as proponents of leading contenders make their case to be the metro or national IoT network of the future. Rick Merritt, EE Times Silicon Valley Bureau Chief, moderators this discussion. Join in and ask his guests questions.