Here is a steampunk style shelf support bracket.  The model consists of pipe pieces just like metal ones, but without the cost!  The only tricky part of the assembly is getting the final pipe in the triangle in place.  To do that I first made sure any remnants of the brim were removed from the end of the pipe.  Assemble two sides of the triangle. but don't turn the pipe all the way in.  Then take the last piece of pipe and screw it all the way into one end, swing the other end into place and screw the pipe into it.  Finally, adjust the pipes as necessary.