Man I wouldn't want to see what one of these people worried about spoilers open up the CE box and see the pamphlet with the code for the DLC, as they will get angry when they realise it tells you was it is and does and not blank piece of paper with no info at all.
I think a REAL spoiler is what actually happens in the DLC, not what it's about.
I have already seen photos and scans of the recently released "Art of the Mass Effect Universe" on the Mass Effect Wikia. I was there as I'm going through a ME2 session in preparation and I saw these in "new pictures added" in the sidebar. Now I know stuff I wish I hadn't, (I'm an adult and will move on). Anyway, beware there is a lot of stuff out there already, showing the DLC is nothing in the scheme of things.