Splashr.com has a neat little tool which lets you specify some topic tags and it then grabs suitable photos from Flickr.com and presents them in whatever way you want. There are actually a lot of choices. You can then view presentation in a popout window or embed into your web page.
Of course, you can pick any topic under the sun. As long as there are some photos with the tags you pick, you’ll get results. You can choose 25, 50, or 100 images for a given presentation (if there are that manny with those tags).
Here’s an example of photos tagged with “car”, “cars”, “automotive”, “mobile”, “travel”. It takes a bit of time for the presentation to be set up, but once it has been, it’s relatively fast.