screenprinting "wallpaper"

I got this idea to decorate a large wall by screenprinting a large floral print over and over in a damask pattern. A friend and I talked a bit about how to do this in an efficient way. Another friend of mine once screenprinted directly onto walls with pretty good luck.

We didn't actually do this, but someday I'm going to! We figured that we could snap a grid onto the wall with a chalk line, and take a screen that fit inside the squares or potentially had two points inside it that would line up precisely onto the square pts. We figure that a totally symmetrical design would be more difficult to work with than something with more organic lines, in case there was any variation from print to print. Maybe it would be good to rotate the image by 90 degrees or 45 every other print. I figure it would be best if the screenprinting ink is water based or water soluble (I've used plain old acrylic paint before) so the first print could be wiped off if it's an iffy print.