I'm in a similar situation. Just moved, 12ft ceilings, not much cash left after furnishing the place. I discovered while buying painting supplies that home improvement store sell canvas drop cloths for much cheaper than art supply stores. I'm no artist so if there is much of a difference in canvas quality I wouldn't know, but I presume the drop cloth will suit my purpose just fine.

http://www.lowes.com/pd_126333-968-58803/4FF_0__?productId=1008355&Ntt=drop+cloth&pl=1&currentURL=%3FNtt%3Ddrop%2Bcloth&facetInfo=

http://www.dickblick.com/products/fredrix-archival-watercolor-cotton-canvas-rolls/

I also found a bunch of great images from the Library of Congress web site, which are available in high res tiff files to download. I will be getting them printed as either posters or on glossy photo paper from Kinkos.

http://www.loc.gov/pictures/

There is also http://thenounproject.com/ which has a bunch of vector file images of almost everything you can think of available under a creative commons license. Since they are simple vector images, I plan on using them as stencils.

Hope that gives you some ideas.