A little different than backlit lettering, but...
I had my girlfriend carve out a stencil on her laser cutter at work so we could spray paint our name boards. She used 1/4" plywood, and we used it to stencil the side panels as planned. We then realized - holy shit, we could use the positives that were cut out out to make the transom name boards. So, we just took the letters, painted them, coated them in epoxy, and stuck them right on the board. Finished up with a few coats of varnish. It looks super cool because instead of a real carving like most of the fancy boats would do, ours stick out.
Back to your question about backlit lettering, I think this would look pretty damn awesome if it was lit from above or below because the letters would cast a shadow - see what I'm saying? Anyways, might be something to experiment with anyways. We were able to use some seriously gold paint too so they shine like crazy.