Holy crap! That's bad times for sure. Like somebody else said thank god it wasn't parked in the garage, of if it was thank god the fire was isolated to the truck. All things considered it happened in as good a spot as possible, could have been while driving, way out in the woods, or while you were leaning over the engine to change the plugs, all would have sucked for their own reasons.
I too would like to see some more hi-res. shots and hear about any sort of new datails as to why that happened. I'd bet on the battery for that kind of spontainious combustion, a short would either have happened when you parked it, or when the fridge kicked on. You didn't say if you had the fridge hooked up or not, but in the time it was parked the fridge would have to have kicked on a few times, and with a still truck not much could have chnaged. I've heard of Optimas going bad before, never quite this catastophicly though.
DiscoNomad, check all your local autoparts stores they will all carry a high end spiral core battery, I run the Exide, I've heard good stuff about the NAPAs also. Also check the amp ratings of the Odyssey batteries, they tend to run significantly smaller per amount of power than a conventional battery, so you may actually be able to squeeze more power into the same space.