If you don't get caught up in the trap of what I call "boring common tubes" you might find some jewels that you can design around. Despite all the hoopla from those who wish to sell premium tubes and ascribe philosopher's stone like properties to them one has to realize that audio is just about the least taxing application for a tube and most TV tubes had to work with higher frequencies where tighter tolerances were a must. DC is the "lowest frequency" that tubes operated at with audio being the next lowest. So signal and power application tubes in the video, vertical, and horizontal circuits work well at audio frequencies the only problem being finding circuits designed around them is you don't do design work yourself. And if you don't it's a simple matter to substitute an "other than audio" tube for an audio one and then play with the components/parameters until you get something you like. Fer example the 6GK6 is identical to the 6BQ5/EL84 'cept the basing is different and the supressor grid isn't internally tied to the cathode. And there are scads of other tubes that are identical to audio ones but uncommon in audio. Get a copy of a later RCA Receiving Tube Manual and perhaps Sidley's "Tube Lore" for starters. After all some of the better known HiFi manufacturers such as MacIntosh used HO (horizontal output) tubes in some of there designs as they were cheaper and more rugged than audio designs. Yeah, more rugged as a TV duty is pretty much "continuous duty" while audio applications are a shorter duty cycle.
With all this said and one you'll probably not be able to use the innumerable damper and HV diodes you've gotten although they do make rugged single diode rectifiers nor will you be able to use the 6EK4 type high voltage regulator shunt triodes (although a few hearty souls have!) and there are a few other classes that aren't easy to adapt but the RCA manual will make these clear. But I've never found any of the output tubes - vert, vid, or horrible - to now work well for audio applications and there are probably some audio specific tubes such as 6AQ5s and such in most TV collections.
For the holiday season you can wire a bunch of damper diodes in series until you equal the line voltage for a low-light radiant heater. If you're careful with a propane torch you can heat them until the vacuum pulls the envelope around the elements and if you slowly cool them you can have a really funky tube heater/glow sculpture <grin>. Oh, while some really hate the idea I've had success using the series heater string designed tubes with the "odd" filament voltages in designs that used the heaters in series across the mains to heat them while using a separate B+ only power tranny to provide line isolation. AFter all this is the heater scheme that the tubes were designed for and they have really high heater/cathode breakdown voltages - this allows you to use odd trannies made for SS applications with voltage multipliers to provide B+. Also most less than common heater voltage tubes (6.3 & 12.6) can be used with a series resistor to drop the heater voltage while those higher can have voltage multipliers and/or odd SS trannies provide heater supply (I've got lots of 18-30 VAC SS trannies that power high heater voltage tubes well).
So your use of these valves is only limited by your imagination.