We have used old bricks, free to us, to make a walkway at our old house. We just removed a brick "sidewalk to no where" in our backyard and have bricks to use again in another part of our property. DH wants to make a little patio with them next to the shed.
We also have used pavers found at a flea market and made more of a "step" way than a walkway. Thank goodness I placed them in the yard based on my stride otherwise DH would have placed them comfortable for his height of 6'6" and I would have been leaping from stone to stone, LOL. When we moved, we took the pavers with us and found a use for them on the side of our garage where we keep the garbage cans.
I've seen walkways made from slate from old roofs, broken up pieces of cement, big tiles and riverrock/large gravel. My brother in law had a beautiful gravel walkway in his back yard. It took some maintenance but it really was nice (and cheap, I've been told).
The city is doing roadwork near our house on an old boulevard. Under the asphalt are original bricks that they are not reusing and are letting people come and have for free (so I've been told). I wonder if people will use those for walkways or just have one or two as momentos?