It seems there's a lot of people who think that images in Wikipedia can be used however they like. In fact, unless they've been released into the public domain, they have licenses that require some fairly minor, but still important, actions if you want to use them.
Below is an email I've just sent to the owner of Sydney Architecture Images: Newtown Gallery, who seems to have taken all the photos from the Wikipedia article on Newtown, without any attribution, and slapped some ads on it. I'm willing to give the person the benefit of the doubt.
Your Newtown Gallery is breaching the copyright of, it seems, all the
images from Wikipedia's Newtown article:
http://www.sydneyarchitecture.com/INW/MAIN-GAL-NEWTOWN.htm
Specifically, and what made me notice, is that you are using my photo:
Images on Wikipedia are not free for you to use without restriction, unless specifically released into the public domain (for example, the Trocadero image you've used). Most of the images on Wikipedia are available under quite liberal licenses, but they do impose some requirements on you.
In the case of my photo, I have licensed it under the GNU Free Documentation License. This license has quite simple requirements, basically that you must attribute the author and license your copy of the work under the same license.
This image that you're using:
is licensed under a Creative Commons license, which has pretty similar requirements.
So in summary, you are free to use these images, but only when you follow the requirements of the license. Please amend your site accordingly.