By way of the always superb BLDGBLOG, I found this website: Old UK Photos. It’s certainly aptly titled, for it displays photos from the Victorian era through the 1960s, often enhanced from black and white. The copyright statement of the website states:

Please note when sending in any scanned images that we can only accept photographs that you or your family have yourself taken, or are of such an age that the owner of copyright has been deceased for over 70 years. Generally speaking, we believe that scans of old postcards are Ok. There is one postcard company – Frith’s – that is still in existence, and therefore we cannot accept any scans of their company’s postcards. Under no circumstances should you send in any images that you have downloaded from the internet. Thank you for your patience and your co-operation.

As you see, the managers of this website take pains to be clear as to what is acceptable and what is not. I rather think that at least in the U.S., uses of photos that do not exactly fit these requirements would be acceptable under Fair Use, but the website managers, like museums, err on the side of caution. Despite these restrictions, what they have accumulated is impressive. The format of the website is perhaps a tad clumsy, but if you have the forbearance, you can find photos such as these:

If you loved these photos, you would love the phenomenal The Empire That Was Russia homepage hosted by the Library of Congress. It has long been a mainstay of Arts & Letters Daily’s “Classics” section. In the coming years, these photos are likely to have ever-greater significance and meaning for those who live either in Russia or out of it. The photos of that collection are also enhanced and seem to be not from just the past, but of any age or place on Earth. I haven’t looked too deeply into them, but they seem to be public domain as well.

Another UK-centered website is Leodis, funded by a grant in the UK to put all of Leeds’ 40,000+ photos on-line to make them more accessible to the general public. The website says:

The largest collection of photographs on the site is the City Engineers collection. These were photographs taken for the City Council from around 1890 to the 1960s of areas of municipal concern such as pre slum clearance or road alterations.

The site seems to be maintained in part by generating revenue from people who want to purchase these outstanding photos. On a more personal note, my mother, a part-time genealogist, tells me that exact photos of my ancestors from the 1800s can be found in this repository. One of my great-grandfathers hails from the town. Unfortunately, unlike the previous two websites, it seems like this one tends to show mostly copyrighted photos:

Unless otherwise stated, the copyright, database rights and similar rights in all material published on this site are owned by Leeds Library and Information Service, Leeds City Council.

Again, that is not actually to say you cannot use them — but it means beware!