So I think I just found a forge Easter egg. I was forging on erosion, and I spawned a large walkway. On the front of this piece, a little beam juts out that looks like a support. This piece So if you look very closely on this arm of the piece, there are two dots. These two dots (front left, back right) These simply look like two dots, but when you hi-light the piece in monitor mode, this happens. Two smiley faces appear. A closer look Am I seeing things, or is that an Easter egg? If so, there might be even more to find.
On Impact, some of the objects have Spartan ID tags on them. I'm pretty sure that the Bunker, Ramp does, but I can't remember any of the others. I think they're Spartan-III tags as well, I remember one being S-243 or something. Reach reference?