I mostly upload my own photos; somewhere under ten percent of my uploads are either public domain material or from sources such as the Seattle Municipal Archives that free-license interesting photos. Here are some examples of my uploads of other people's work.
I uploaded and annotated the contents of a rather remarkable 1900 booklet called Seattle and the Orient. Amazing stuff (although the "and the Orient" in the title is mostly a business pitch.)
The old King County Courthouse on Profanity Hill
The Waltham Block: this now houses the Davidson Gallery and the Glasshouse
The Terry-Denny Building (at that time The Northern Hotel), still there (on the west side of First just below Yesler)
Looking west on James Street toward Pioneer Square; the two buildings in the foreground still survive, as does part of the second building from the right, and a few that can be seen in the distance (though, sadly, not the Seattle Hotel, second on left, or the Olympic Block, dead ahead).
Railroad Avenue along the downtown waterfront (now Alaskan Way)
Centennial Mill (flour mill at the foot of Yesler Way)
Tinfoiling Rainier Beer bottles
Inside the hull of a ship under construction in Moran Bros. shipyard
The Seattle Room at the Seattle Public Library is an another great resource. Among the many things I've found there are:
A 1905 Rainier Beer ad from a Polk's Directory...
... but I think this one from The Argus Alaska-Yukon-Pacific Exposition special issue (1909) is even more fun.
An 1899 ad for Heckman & Hanson Shipbuilding Co.
A 1904 map showing the route of the Duwamish River by Georgetown and South Park before it was straightened
An 1893 map showing the old street names in what are now Wallingford and the University District
Elements of this 1912 photo from the Seattle Post-Intelligencer...
... were photo-collaged (part of it reversed) and hand-colored on the cover of this 1915 book.
Seattle's first (horsedrawn) street car at Occidental Avenue and Yesler Way, about 1884. The view is across Pioneer Square. The building in the background stood on the present site of the Mutual Life Building at First Avenue and Yesler Way. The building on the right was the Occidental Hotel, destroyed in the Great Fire (1889), replaced by the and the Seattle Hotel (which was demolished in 1961 and replaced by the "Sinking Ship" car park.
The SS Tacoma under construction, one of the fastest steamers in the Puget Sound mosquito fleet
And from some other sources...
Pioneer Square, Seattle, circa 1906. Rob Ketcherside actually found this one & uploaded it to Flickr; I brought it over to Commons.
Seattle's old waterfront fire station, replaced by a new building in 1917 and again in 1963. From the Municipal Archives.
Seattle City Light Director of Home Economics Mary Norris, 1954. From the Municipal Archives.
Space Needle under construction, 1961. From the Municipal Archives.
Looking through the 1909 Tyee (University of Washington yearbook), I came across some wonderful cartoons and drawings by a man named Olaf E. Caskin, who I gather remained in Seattle and worked mainly as a commercial lithographer. I've uploaded a number of them in Category:Olaf E. Caskin illustrations in 1909 Tyee. Here are a few of the best. And remember, this is 1909: years before Will Eisner.