The idea here is to design and build something useful, unusual, compact and not too greedy for power.
I've got a few American metal tubes of the 6V6, 6F6, 6L6 variety which, though less popular than the later glass versions, are decent valves with a quirky look.
To keep with the black minimalist look of these valves I've chosen a black drop through mains transformer from a McMichael wireless a black tar dipped transformer from a 1939 Philips wireless. This set had an AZ1 directly rectifier (4V @ 1A header) and EBL1 pentode (6.3V @ 1.4A). For output transformers I've picked a couple of tiny ones from Philips wireless sets - these were driven by EL41 pentodes so have the correct impedance when driving 4 ohm speakers, albeit at very lower power.
Here's a rather complicated one using ECC83 (I'd use 6SC6) and 6V6. It's DC coupled, and has two negative feedback circuits - which is unusual.