Do you have a creation myth?

Do you have more than one creation myth?

Do you have any objection to blatantly ripping off Greek myths and legends? We could take some of the more obscure ones and alter them slightly to fit your culture. This would have the added advantage of seeming familiar, while not recognizable. (We could mix and match cultures too... Norse, Gaelic, Arabic...)

I don't know much about your world, but here is how I would (maybe will) think about it if it was mine: Is there more than one sentient race in your world? Maybe they each see images that pertain to their own culture, and see a figure resembling that of their own kind. If they worship gods (as opposed to God), the one resembling one of their own race might be viewed as a god or demigod or something...I might also take a random thing (Icepick, spear, spoon...) and make up something ridiculous (the cow jumped over the SPoon ), then try to make it sound cooler, and use whatever I come up with if it seems good to me. You could also use these ideas to make children's fairy tales for your world (kind of a weird concept, but one I happen to like).
I hope this helped, God bless you as you work on this.

I think RunningWolf has the right idea. Having just read a little about a few of your races, I think you have a rich background in them from which you could draw names. What kind of objects & artifacts would they interact with on a daily basis? Maybe a near-straight line of three stars above a distorted field of stars would be "The Hammer and Anvil" for the Haethor, and "The Net and Spear" for the Sivanis.

What role does each race see itself as playing in the universe? What kinds of stories would they tell their children? Without even fleshing out the story too much, you could come up with a name for the hero in the fashion of that race's language. If they're like us, they'll name some constellations after their heroes, where the constellation could look like something from the hero's story, or just a human-shape projected onto a few bright stars.

As for the two bands of the galaxy...I'm not sure what you mean...how can you see two bands of the galaxy in the sky? Unless your world is a significant distance above/below the plane of the galaxy (or the galaxy has a very unusual shape), I don't see how you could have more than one band in the sky.
But anyway, if you have two bands of the galaxy, I imagine they could end up having names connected to any of the classic dualities of existence...Life/Death, Good/Evil...even Male/Female? If one band is visibly bigger/brighter than the other, they could be "The Greater and Lesser [X]". (X = "Heavens"? "Eyes"? "Clouds?"). Maybe they could be called "[Y]'s Tears", where [Y] is some deity they imagine would cry twin streams of tears across the night sky.

For the card game, perhaps decide on the single word that best describes the game, and then poke around thesaurus.com looking for archaic/unusual sounding synonyms?
Edit: starting from "Magic" and thinking about trickery, I came up with "mirage", "snare" and "charm" as candidates.
"Anyone up for a game of Snares?"