While I would say "welcomes", I'm sure I read that both are acceptable. I think in American English "welcome" would be used, in the same way that they would say "Barnsley is in second place".
Depends on how you see Barnsley fc. Is it a collection of people, or a single thing? If it's the former you could get away with it I suppose.
That's true, and that's something that has also always bugged me about the white seats in the East Lower. There's no "." after the "C". If you need one after the "F" you need one after the "C". Not hard to get it right, but it's been wrong for 20+ years. The sign is still wrong, even if they put the "." though.
Other than the missing dot, I think it's right. Barnsley FC, in this instance, are a collective who represent the club. The stadium or Ltd company or whatever inanimate object the club is, is incapable of welcoming anyone. People welcome other people. In this case multiple people.
It's technically wrong, but I'd probably write it the same in this context. Likewise, there should be a point after the C, but if it were up to me I'd just drop the one after the F. Definitely looks more odd having the one that it would if they'd gone for either none or two though.
Legally, and grammatically, the club is a distinct entity. If everybody employed by them* was sacked tomorrow and replaced by new people, the same club would still welcome visitors. *everybody employed by *it* I suppose! Hoist by my own petard....
I've had this discussion many times, in German. Over there, the rule is strict - a football club is singular, so you would say "Hamburg FC welcomes you". You would also say "Hamburg FC is winning". In English, I believe it depends on the context. If you are talking about the club, it's singular, so "Barnsley FC welcomes you". However, when referring to the team, most people regard that as plural, and say "Barnsley are winning". It just doesn't sound right to say "Barnsley is winning". And there should obviously be a full stop after the C as well. That bit looks very strange indeed, and totally wrong.