This website allows registered users to upload scanned historical images of architecture and map them. Visitors see thumbnails of the images on a map. You can click on the thumbnail to bring up a full image with information and then click on that image to get a larger one, which is big enough to use in PowerPoint. Note that, on the page with the smaller full image, there is a box towards the bottom with a permalink. This is good to note in the image title, PowerPoint notes, or elsewhere so that you have a record of the image source.
It is helpful to visit the “How to Use SepiaTown” page before delving in too far since there are some interesting features that may not be initially obvious. Two examples are the figure on the map that shows the location of the photographer and direction of view and the “Then/Now” button that shows a contemporary street view from the same perspective. Images for many cities from around the world have already been uploaded.