Same here, lot's of pictures, some that will never see the light of day or at least be seen on the internet. When Greg Swingle was shooting video while in my hangar I had to caution him on that, some embarrassing, some that other's may think were just "wrong" for various reasons.
That brings up the need for a easy way to mount the pictures, and though I know many have all metal hangars with maybe that white blanket type insulation, I feel the need to stick to good old fashioned stick framing and then interior finished with OSB. Now you can put any new picture up with a staple gun, simple. My one bare concrete wall that adjoins my shop foundation just got framed over, insulated, and sheeted this winter, mostly because I was running out of wall space and didn't have stapler that worked on concrete. If I had a metal hangar I'd have to throw some framing up just to hang some OSB just for picture hanging, it would be easy to do.
I just got through last fall building a crane "hangar" in town on some commercial property I bought. Just big enough for the crane and any newer one I might aspire to, 14'H x 40' long and 18' wide. I wanted to keep it heated, that was a given, but mostly just keep it in the mid 40's to lower 50's at most. After briefly thinking about it I went full concrete foundation as per a house, with perimeter foam insulation well below grade and an insulated radiant heat floor slab. Stick framed and OSB up to 8' on the inside, tin roof and walls. I'm heating with a 2500 watt electric boiler with the thermostat IN the slab, and set at 50 degrees. There is a reason most homes are stick framed and sit on a concrete foundation, they work well thermally and are cost effective. Pole barn types and metal buildings are great also, until you want to keep them warm or cool, just like a mobile home compared to a house on a basement.
I don't have a beer fridge or many of the extra's you guys mention, but then again the shop is right upstairs and the house 35' away so I kept the hangar pretty business like, other then some tractor implements, a small flat bed trailer, and a little lumber that's all. As a result I built it just 28' deep and 40' wide, so cheaper and easier to heat. With my strip it is unlikely I'll ever be flying a bigger plane then something like what I have now plus I have a big shop and other out buildings for junk so I kept the hangar "just right"