Don't have any pics, I took a computer shipping box, packed it full of old clothes. I tried to use as much blue jeans and thicker materials. Taped it up real good. I have card board inserts that are the same size as the box. As the box gets worn out, I'll tape another layer on it. Used it quite a bit this summer, and never had an arrow go through it.
Several years ago I found a large styrofoam billet washed up on the banks of Allatoona. It was a large square about 5 x 5 x 18". I wrap a tarp around so it doesn't look so bad in the backyard. If you could talk with a dock building company around one of the local lakes they might hook you up. Mine is pretty old and still works great. I put my block on an old milk crate in front of the billet
My dad and I made one from thick outdoor carpet and 2 4x4 posts. Set the posts fairly wide then wrap carpet. We made ours about 6 foot tall and 6 feet wide. I was shooting recurves 50, 70, and 90 meters back then so my arrows weren't exactly screaming by the time they got to the target.
If anyone is close to lincolnton I probably have some old floats you can have I've been building Docks for 10 years just pm me your welcome to them. Also as said above I've also made a target out of old clothes and if you could find something to put them in that wouldn't wear out so fast it would be the best target I promise ya you want shoot threw it.
When we had a public archery range hay bales lashed together were used for backstops.
After it closed I retrieved some large pieces of styrofoam out the marsh.
I lashed 4 pieces 36"x18"x8" (approximately) together and filled the holes and cracks with expanding spray foam to make a 36"x36"x16" backstop.
Repairs are done with more spray foam.
A friend of mine had a neighbor that draped a thick blanket or comforter over a rope stretched b/t 2 trees and put his target in front of it. The loose blanket supposedly caught the arrow if he missed his target without letting it pass thru completely. Have been saying I was going to try it but haven't yet.