I doubt this is a highly used feature in Photoshop CS2, but it can be useful at times.

First, you want to open up your images in a new document:




Most likely you want to match an image to the background so be sure to have that layer selected.




Next, Image > Adjustments > Match Color...




Now, the source is the title of the document you're working on and and the layer is what you want to match the image to.




Finally, you can mess around with the sliders a little bit to find something you like.




Then you get your creative genuis working and...