I havce built many permanent (actaully semi-permanent) tree stands. We have 6 at our hunting camp and I have one at my house (as well as to totally permanent ones). I don't think I have digital pics of the stands, so I will try and explain (may have to charge a small copyright fee ). The stands are self supporting and nothing needs to be nails into the tree and they can be moved in needed. Basically 2 components - a ladder and a platform w/ seat. We use 2x4s for the ladder (most are only 8', 1 is 10'). The platform is framed with 2x6s and has 5/4" decking with a built in seat made from scap lumber (mostly 2x4s). Everything is treated. The platforms are either 4' wide x3' deep or 3'x3'. The ladder attaches to the front of the platform, is braced to the deck, and is slightly angled to ease climbing. The back of the deck sits flush against the tree. Most have a make-shift railing (2x4s) attched so we can lean guns against or hand gear on and to hang como burlap from. To hold the stand in place a chainis connected to the front face of the deck with an eye bolt, holes are drilled thru the back face to pass the chain thru and the re-attached to the underside of deck with another eye bolt. We make the chain as tight as possible by hand and them tighten the nuts on the eye bolts to tension. An wahla - your done. The construction is fairly simple once you get going. I came up with a "blueprint" one day and it has since been modified a few times with every new one being a bit better. We have assembled them totally and dragged them to the woods with a 4wheeler and have carted them out in 2 pieces and assembled in the woods.

Final thoughts: These stands work great for us. They cost about $100 if you buy all the hardware and materials. we use a lot of scrap lumber and the cost for some was only a couple 2x4s and the hardware (~$25). They are solid as a rock and roomy. I am a big guy and don't feel comfortable in a tree on something without some heft and room. The 3x3 is a bit camped but ok. They are heavy and take 2 men and a boy to put up. Anything over 8' you will struggle to get up without a block & tackle or some other way to raise it. My friend built some rather high ones (16'+) and used a backhoe to set them up. And like I said, they are portable (i have moved one already), but you probably would only do it if absolutely necessary.

note: i like these a lot better than permanent stands, mostly because there is less maintenance. As the tree grows it pushes out nails, boards, etc. and will eventually ruin the stand. With the other type, all you need to do is loosen chain every year or 2 (not more or the chain will grow into tree) and adjust the stand if necessary and tighten chain in the fall. Also nice to not have to run nails into trees.