I've posted a '98 lugged steel frame in here, and it was pretty well received.
It's the last year lugged steel was offered by the maker, and the frame was probably built by DeRosa (it's a Primato clone).
Technically, that's not yet a venerable frame, or vintage.
However, the lugged steel frame was built up as a dream bike boom racer and a case of form follows function.
But if you consider there's a page on this forum called Vintage Mountain Bikes, which essentially are all from the 90s, then the topic gets a little leeway.
For my personal perspective, any bike that would be accepted on
Classic Rendevous google groups, or is represented in
Classic Lightweights should get to play, and that certainly includes bike boom bikes.
Age wise, aero brakes and indexing are probably pushing past the spirit.
Aluminum bikes, unless they're classics like Alan and Peugeot are probably dicey, thought even early Canonndales are going to have a fan club, and there are a few posted here.
If it has a Sturmey Archer drivetrain, everybody wants to see it, especially now that they've closed their doors.
I think a topic like, I found this cool bike and don't know anything about it, is always acceptable.
But setting one's limits on others is a control-freak thing, anyway. .
If you have something cool to show, we'd love to see it. .