The others more or less got everything.
Stars are about as important to Komari as they are to Yumemi and very much in a similar vein. Stars are a running motif throughout her character arc: the rooftop stargazing scene, Rin’s wish, the Little Match Girl story. It’s representative of her hopeful nature which you can tie into her personality, the theme of her route, and a theme of the overall story of Little Busters!.
The others got Rin’s ribbon. IIRC, we learn either in Rin2 or Refrain that Kyousuke gave her the ribbon, so it serves as a symbol of their relationship as siblings well. I feel like there was more to it, but I can’t remember, and I feel like that bit I’m forgetting answers why it’s a bell as well.
Haruka and Kanata’s symbolize their relationship as sisters both because they have matching accessories and because the accessories are made of two balls. This is similar to the symbolism of the egg in Haruka’s route. This is also similar to Kyou and Ryou’s ribbons in CLANNAD.
Like HeliosAlpha said, Kud’s bat is symbolic of her status as the foreigner as well as what that means to the team which is explained in the fable. You can also bring her hat and cape into the mix which represent her relationship with her mother with the colors likely being representative of Tebwa’s national colors.
Mio’s is the most plain of the hair accessories as it’s really the only normal one if you think about it, so that’s fitting. I wanna say it is red because red is the most visible color on the color spectrum and it serves as sort of an ironic contrast to her tendency to blend in with the background, but this would also fit Midori’s tendency to do the opposite. I came up with more to hers while I was reading her route, but I was so into it that I forgot to write it down and forgot. If @HeliosAlpha has more, I’d love to hear it. 
Sasami’s ribbons are meant to make her look like a cat. I can’t remember where, but I remember there being a specific scene of her in a cat pose with her silhouette made to look exactly like a cat on the wall behind her, and it was a really unsubtle clue into that. I can’t remember where it was though. I thought it was in either the OP or the ED of the anime, but I guess not. It might have been one of the box arts from the BDs or maybe it was in the anime, but not the OP or ED. This one kind of serves the same purpose. There are probably tons of ways you can interpret her relation to cats (aside from the obvious cat of her route) in terms of the nature of cats, what cats have meant or symbolized historically, superstitions and so on and so forth, but I feel like that’d make an interesting write up for another post on another day.
Saya’s is the only one I’m legitimately clueless about. I feel it’s something that would have to be found in the EX VN rather than the anime because after watching the EX anime twice, I couldn’t come up with anything (or maybe I just wasn’t paying enough attention), and I seriously doubt that this character as Maeda’s favorite of the bunch would lack meaning here when all of the others have some meaning to derive. Why does she have two different kinds of ribbons? Why is one black and two white? Is there a reason for her having three in total? Is there a reason they’re opposite colors or do the colors symbolize their own things? Are their placings (white on top, black on back) relevant? I have no idea, but they’re all questions I plan to keep in mind when I’m able to read her route in EX.
Kagari wasn’t meant for anime!
