I can't even remember what this photo is of, but I like the colours. The midtones are the area I especially like where the purples come out and the little bit of green. I also quite like the random light on the left hand side – it makes it feel less pristine.
You can download these free to use hi-res photos here
I really like this image. You can't quite tell what's going on but there's movement, a metallic quality in the bubbles and a lovely sense of depth.
This is a very simple long exposure photo, but I love the depth in the image. This sense of depth comes from the thickness of the lines as well as the brightness of the line. Could a site use these principals to create hierarchy?