I have a stash of posters and old calendar pictures, sorted by subject (animals, space, religious, art, plants, and other).
Ever since Mxyl was a toddler, we've always put up interesting pictures at his height, so we'd always have something interesting and/or beautiful for the kids to look at.
At this point, I have a lot of pictures (word gets around when you want old calendars!) but I only think to cover the lower walls occasionally, now that the Zoomlians are bigger.
That's a shame, really, because the older kids always enjoy looking at the more complex posters. The vertical poster in the first picture is a replica of the "time column" which still stands in the Natural History museum.
It's a bit out dated (I saw it when I was a kid!), but I was amazed at how helpful it was in representing when the different creatures existed, and the increasing complexity of life. I just bought an updated poster.
We also made this mural to put the drawn dinosaurs on. It's from my big roll of paper, maybe 4' x 8'. The sky and
And the rest of the projects were lots and lots of reading from this random library selection, and packets copied from Dover books Dinosaur stuff.
We also did a bunch of their stickers, and some of the invisible "magic" picture books - a huge hit!