I think one of the cheapest ways to add some art to your home is to make your own. I purchased these canvases at Hobby Lobby for about $16/piece and used left over fabric from my lampshade makeover to create two pieces of bird art.
All I did was google images of bird silhouettes online, choose a couple that I liked and sketched them onto the back of the fabric. If you aren't comfortable with your own sketching, you can always print them out and trace. I carefully cut out each bird and used Mod Podge to attach it to the canvas, then once it was dry, I used another layer of Mod Podge to seal it.
I originally saw this piece of bird art at Houzz.com and it is what inspired me to make my own. If you love decorating or need decorating ideas, I cannot recommend Houzz.com enough. Someone introduced me to it a few months ago and it is an amazing resource to get ideas.