Very well done, RobA.
That thing looks like you could drive semi's over it. You have a challenge to take some of the clinical highway look out of it and create some kinda natural woodsey look. I fear that any kind of metal or tubing might take it in the wrong direction. I think that chunky timber is the best move. Chunky (like 6 x 6 and larger) simply to play off of the concrete mass, and timber to soften the same concrete mass.
