I can envision a mirror setup maybe 10" X 14" you could slide up to the back of the amp. You could get creative with a hardwood base and some brass rod from a welding shop maybe? Angle the mirror slightly forward until the tubes are in clear view from your listening position.
I could eat up a couple of weekends working on such a project. I think mood lighting is very important when listening to music ... I have a couple of neon lights in my little man cave. On rainy winter nights I get a fire going and flip on the neon. Couple glasses of vino or a few good NW beers and I am ready for tunes.