[...] of course, there’s Tantsu and Satula, both by Marimekko. Oh, how I love them. I wrote a haiku about them last [...]

This is the contact info for the Chicago distributers of Marimekko.
http://www.marimekko.fi/MarimekkoWeb/Templates/ShopSearch.aspx?NRMODE=Published&NRORIGINALURL=%2fENG%2fshops%2f&NRNODEGUID=%7bD199575C-5A29-4653-A7A6-8F208918B686%7d&NRCACHEHINT=Guest

Check out these posts, Design Sponge was trying to track down that same print I think and was able to get some through the company. I hope this helps. If this link doesn’t work, just search for Carrie on her site.
http://designsponge.blogspot.com/search?q=carrie

Good luck!

Kiitos Marimekko carries Tansu in pink, but I haven’t seen Satula anywhere. However if it’s available to order I’m sure Kiitos can help you.
http://kiitosmarimekko.com/marfab.html

About the picture rail, in homes of this period most often the wall would be papered or painted below the picture rail, and then above it would be either a different paper (like a scenic border or larger version of the wall design), a stenciled design, or just paint, either the same as the ceiling or an accent color. (If the same as the ceiling, usually the ceiling would be a color, not stark white.)

Regarding the wallpaper question, don’t forget about fabric as a (cheaper) alternative to wallpaper. (The marimekko might not be cheaper than wallpaper, but you know what I mean.) Sites like reprodepot.com have fantastic fabrics that would work so well as wall treatments. Just something else to think about.

(Here’s an article on how to apply fabric to walls–it’s just like putting up wallpaper, only with starch instead of wallpaper paste. You might need to recopy this url because it’s super-long:
http://www.hgtv.com/hgtv/rm_walls_other/
article/0,,HGTV_3805_1375532,00.html )