refs

Architecture (ancient/medieval ) : https://archaicwonder.tumblr.com/

space/industrial area : http://ralphmirebs.livejournal.com/219949.html

Hard surface : https://hardsurface-blog.tumblr.com/

Weapon : https://weaponslover.tumblr.com/

Medieval Armor : https://gumroad.com/daviblight#

Airforce : https://titanium-rain.tumblr.com/

Nasa (2400 images) Creative common from Flickr (collected and compiled by the Generous Reid Southen):

https://reidsouthen.selz.com/item/54a86fa6b79872193c1d63b3

Moon and Deep Space Exploration : http://planetary.s3.amazonaws.com/data/change3/pcam.html

Navy Ships : https://gumroad.com/l/SPWbn


Technology (60's) : https://www.flickr.com/photos/lordolsen/sets/72157665494083246

Reddit : https://www.reddit.com/r/sfwpornnetwork/wiki/network#wiki_organic

Machineporn : https://www.reddit.com/r/MachinePorn