Nice job. You have an eye for the reality of how an object should be built. That is to say that the biggest issue I see with beginers is they're poor concept of how an oject is built in the real world.
For example: Everything in real life is not built with 6" X 12" wood or metal beams.
Up for a challenge my friend? Use this frame, and add a catwalk, and support structure. Remember to try and keep your parts in realistic perpective to the existing frame. And keep in mind that the lower you get to the ground the heavier the structure must be to support the lighter elements that are built on top of it.
I like this. And as this is your first, keep going, I'd like to see more of what you can do.
So get to work mister!

your pal Cosmic.
Back from the Wasteland.