Loving this so far, but a couple of things that immediately caught my eye:
The LaunchBox main menu font is tiny.
The muted colors on unselected items is what I love the most about the theme, but I'd argue you could take it even further -- make them full grayscale. It would make the selected platform/game stand out a more.
The small spaces between platform banners look weird with the grid pixels showing through. A solid color background would look better IMO.