Here is an idea or two for cheap art appreciation:
1.) If you go to used book stores you can always find art books (you know the really nice coffe table books) really cheap.  Usually these are oversized and have nice large prints.  I buy these if they are a couple of dollars and then bring them home and tear out the pages to hang all over the house. 
2.) If you are in a retail bookstore don't forget to check their bargin books too.  A couple months ago Borders had a huge book on Escher - one of our favorite artists.  It was about 15x15 and the prints took up the whole page.  It was on sale for $8.00 and I got it even cheaper with the teachers discount.  Out of that book, we got over 80 prints for less than 10 cents each.  It will be so hard to tear apart that nice hardcover book but it is worth it!  Art books are the only books I take apart!  The art gets more attention if it is hung on a wall as opposed to sitting in a book that might not get looked at very often.
3.) Use art postcards.  Let the kids pick out their favorites to mail to family and friends, hang them by their bed, make collages out of them, use them for matching or go fish games.  They are usually sold in books of 6 or 12 and are only $1.00 to $1.50.
4.) The web has lots of neat sites too.  Here are some of my favorites:
http://www.nga.gov/kids/zone/zone.htm great software to make your own masterpieces
http://www.eduweb.com/pintura/index.html neat mystery to solve using art
http://www.tate.org.uk/detective/mysteriousobject.htm another mystery to solve
http://www.moma.org/momalearning/artsafari/index.html an art safari
http://smartmuseum.uchicago.edu/smartkids/index.html cool games

Let me know how you incorporate art appreciation into your home - leave an idea below.
Enjoy!  Dee