I think the overlapping spheres being symbolic of an eclipse is too easy if you view it objectively -- they are trying to tricks us. Yes, I always assume writers are trying to lead you astray. So I choose a more subjective approach. The Fade and the World. Magic comes from a weak connection to the Fade, after all -- you bend reality to your will. Creation, therefore, would be exponential if the two weren't separated by a veil. Life, if you will.
Bioware writers like to be tricky, but I wouldn't go and say that they put red herrings everywhere
Too much of that and it would become counter-productive.
Eclipses were always pretty significant, be it in reality or in fiction, and if anything, I've noticed BW doesn't stray from using such popular elements in their stories (magic/life = song is another good example, as is red=evil-ish/angry/dark and blue=mysterious/good-ish/god-ish).
We also know that eclipses WERE mentioned, in relation to none other than Fen'Harel:
I'm on board with this. The other time we heard about an eclipse was from the Black Emporium:
"Two shadowed spheres, an eclipse as Fen'Harel stirred".
It would be especially symbolic in case of Fen'Harel, who, as I explained, draws a lot from Nordic myths about Fenrir - and Fenrir (or its offspring) is known to bring about Ragnarok by swallowing the sun. It could be beautifully symbolized by eclipse as well.
I also wouldn't be surprised if sun didn't play a special, if not literal role in perhaps powering up the Veil? Maybe this is why Veil may be thinner by night, or why Fade and Beyond has been symbolically equated to 'night'. So if eclipse happened during the day, and 'night' happened, it may disturb the cycle. It may also - symbolically or literally - temporarily merge both Fade and Thedas, which may help someone accomplish things that are impossible otherwise.
The ones that looked like companion cards. I was out for a solid week playing Descent and other things though, so I missed if it'd been covered here. I answered my own question though when I went searching to find them for you. Ponytail one was a sneak peek of this! -> https://twitter.com/...801979279736832
Oh, that's just Pala, a new Multiplayer character
I don't think she's in any way significant, when it comes to story itself.