Victory! I'm reading your post.
You're right, you could use any medium. We have used craypas on black
paper, and we have used mixed media with texture sheets/crayons on the
buildings, colored pencil for tiny things, lettering, etc, and
watercolor resist or wash in areas. A few bright markers here and there
are not bad either in mixed media, as long as they don't go crazy with
them. Only problem with markers is that they do fade over time. I have
seen such great things with this project. I would heartily recommend
it to grades 3 and up. I had one boy do his baby brother as a giant in
diapers, crawling on a freeway, picking up cars like blocks and playing
with them, as well as a huge variety of flying animals, giant sea
serpents arising form the waters on a wharf in a seaside town, and the
Metropolitan Shoe collection (can't think of the title of that book
again, drat!!) is a great resource to use if someone wants to draw
really interesting shoes and legs on a giant, maybe let the giant reach
into the picture with a hand to pick up a person, building, train, etc.
LOADS of fun here. Kids get really engrossed in these drawings. We
spend about a month on them. You could stop with the drawing part if
you don't have time for more. My kids start out in light pencil and go
over them with skinny sharpies. Then we proceed to mixed media. If
they draw on black paper, I'd start with pencil or chalk and proceed to
craypas/colored pencils. Though I want to do almost all new projects
this year, this one is a keeper. It teaches them so much about
overlapping and they really get into the idea of freeways/trains that
are elevated, passing behind or in front of buildings. They like adding
bridges (the Bridges book from Dover is a great resource for that), and
we spend a lot of time talking about variety of sizes/shapes in
buildings/doors/windows. There is as much in this lesson as you could
put in any lesson if you want it to be so. Anything that keeps kids
drawing so intently for days on end is worth it's weight in gold to me.
This is truly captivating for kids, year after year.