Cover the columns; isolate the metal frame; wood paneling

Most of the van interior will be covered in wood but some areas will be exposed metal. 

I found this guy who described how to cover the columns in the van:

https://www.youtube.com/watch?v=rWV5kGyDb0Y

I bought a cheap fleece blanket and used it for the first layer:

I used a spray adhesive to attach it to the exposed areas.

Then I used some denim weight fabric I found at Walmart, of all places, to cover the fleece.

After adding the wood. We used tongue in groove 5/16" thick knotty pine paneling from Home Depot to cover the ceiling and walls. Initially we were going to run it front to back in the ceiling but realized we could do it without seams if we went side to side.
Also note how we boxed out the small windows. There is a nice little shelf created. We've got some battery operated USB chargeable fans that we can put in those windows to increase air flow on hot nights.

I used a similar technique to cover other spots that wouldn't get wood covering.

Insulation is Havelock Wool. We used 4 boxes of their wool batts. Some was torn into bits and I used a chopstick to stuff into small holes to fill all of the air spaces. It was time consuming but worth it.

I kept the other batts in place using some 6" tulle but string or yarn would have worked.

We installed shelves near the ceiling to create storage space. I installed hooks under the shelves to hang tote backs for more storage. 

Also note the Coolmax silver insulation on the wheel wells. We also put pieces of Coolmax all of the wood support pieces in the walls and ceiling. This is to prevent direct contact of wood to metal which would be a conduit for heat transfer and moisture control. More about that here at Far Out Ride. This site is rich with information about how to complete the van build including plumbing systems which we did not do. We spent a lot of time doing research in this site and learned so much.