The biggest news out of Agents of S.H.I.E.L.D. over the hiatus between Season 3 and Season 4 was that the legendary Marvel character known as Ghost Rider would be joining the team. Some Marvel fans were disappointed when they learned that the Ghost Rider who would turn up on the show would be Robbie Reyes, who is actually the third man to go by the name of Ghost Rider. The original was Johnny Blaze back in 1972, and the latest episode of S.H.I.E.L.D. included an awesome nod to his comic origin story:
The opening scene of the most recent episode was a flashback that saw Lucy and John searching a dark basement for the mystical Darkhold that had been hidden by the owner who then passed away. Lucy and John found the book, but that wasn't all that they found. Hanging on the wall of the basement was a poster for Quentin Carnival.
Fans of the Ghost Rider comic character would have immediately noticed the poster advertising the carnival that featured Johnny Blaze in his days as a motorcycle stuntman. Johnny worked for Quentin Carnival before he became Ghost Rider, then returned a few times after getting his powers. He attracted too many villains to stay around in the long term, but Quentin Carnival was a key setting in a lot of Ghost Rider stories.
There are really only two possibilities why the Quentin Carnival poster was included in Agents of S.H.I.E.L.D. The first is simply that the show wanted to include a Johnny Blaze Easter Egg for comic fans who knew the whole history of Ghost Rider. Johnny Blaze is by far the most famous of the Ghost Rider incarnations; even a minor nod like a poster for his carnival is a fun addition.
The second possibility has grander implications. The poster could be foreshadowing of an upcoming appearance by Johnny Blaze on the show. Agents of S.H.I.E.L.D. didn't go into detail about the person who owned the house and posted the poster. It's possible that the previous owner was either a fan or a worker at Quentin Carnival, and there's no way that somebody connected to Quentin Carnival could show up without having some sort of relationship to Johnny Blaze. It's a stretch, but we could eventually get to see Johnny Blaze show up in Agents of S.H.I.E.L.D.
Obviously it's too early to say whether or not the original Ghost Rider will appear on the series, but it's worth noting that Robbie Reyes was chosen as the S.H.IE.L.D. Ghost Rider because of his family connections. The show could have used Johnny Blaze, and so there's not necessarily anything to stop the show from bringing the character in, even if the TV incarnation is different from the comics.