For the outdoor dog that we used to have, I made a bed/bag out of burlap that I bought from Joanne's and filled with cedar chips. Had to make a new one every year in the fall.
Later, our indoor dog preferred rugs. He was large for a house dog - 60 pounds. I bought the inexpensive nylon braided rugs from Wal-Mart. Used crochet cotton and whipped stitched two side by side then layered with two more stitched side by side. Then stitched (by hand) big stitches around the edges to hold together. When too yucky with hair - threw away and bought more. Back then they were $2.50 each so for $10 got a nice clean doggie sleep rug. He liked to really stretch out when sleeping. Even the largest bed we could find to buy was not large enough because he would rather stretch then curl up. They have such personalities!
I imagine old jeans would make a good bed but wonder about the seams being uncomfortable. Maybe you should just browse the indoor/outdoor fabric area at Joanne's and see what would be easy to maintain.