I was really, really bored
And it's all nicely linked to each fic, too. (With the obvious exception of Either Way because I haven't finished it yet.)
Each letter of "Fiberglass" is a different character:
F - Jen
I - Ruki
B - Ryo
E - Terriermon
R - Takato (Biomerging, which is why he looks weird)
G - Kai
L - Shuichon
A - Jaarin
S - Juri (who barely features, but Takato mentions her a lot)
S - Hirokazu and Kenta (I was running out of people xD)
Each fic title is in the 'handwriting' font of whoever narrates it. Either Way is a parallel narrative from Ryo and Ruki simultaneously, so the title for that alternates between their handwriting (starting with Ruki's). Strangely enough Ruki narrates the most fics in this continuity - three and a half - but of these, two are drabbles anyway. It should come as no surprise that Takato, who has little to do with the love triangle, narrates the least - one. Ryo comes runnerup with one and a half, while Jen narrates two (though Fiberglass is pretty damn epic and should count for at least five).
The dates are indeed when each fic is set, which makes the series set in 2003 in my personal fanon.
Kai's agent made a convincing argument as to why he should be in the first line of co-stars and smack bang in the middle of the Lee family, namely that Kai co-stars in a considerable chunk of Fiberglass Slipper and provides a bit of drama and helps develop Ryo's character. Or something.
Rinchei is rather bitter that his agent couldn't wrangle the same deal, and so Rinchei and Lopmon are the only members of the Lee family who aren't billed on the poster. :D Jiangyu and Mayumi make it onto the poster because they have a fair amount of influence over events (picnics up trees, anyone?), while Shuichon makes it on because she seems to sneak into Jen's narrative even when she's not on screen.
Terriermon and Renamon both use their Tamer's family names because they're considered part of the family. Guilmon, while similarly considered part of the family, doesn't use a family name, because Takato says they're closer than family anyway, and unrelated friends don't usually have the same surname. Cyberdramon would refuse to use the family name if Ryo ever offered it to him, and makes it onto the poster purely because of his role in An Easy Mistake. Renamon barely features but makes enough cameo appearances to make it onto the poster (and has a really good agent). Guilmon has a decent role in particularly the Okinawa arc of Fiberglass Slipper, while Terriermon has a fairly chunky supporting role through the same fic and An Easy Mistake, as well as his voiceover cameo in A Blunt Reckoning.