Amazing how long my bookmarks list is... the unsorted end of it is getting shorter, though.

A large collection of images, although not very searchable and not very straightforward to use (in my opinion, at least) is the Digital Imaging Project with art and architecture (mostly architecture) from North America and Europe, from prehistoric to modern times.

Kornbluth Photography (documenting the Luxury Arts) has photographs from a multitude of objects. The site is not searchable, and it was last updated in 2014, but does have spectacular images of objects from different periods, places and cultures.

The Database Machine Drawings is exactly that - you can search for machine drawings from 1235 to 1650. There's even a carding machine and several spinning mills in there, if you are textile-inclined.