The best way I can think of to do this is to use a disjointed rollover in Fireworks the idea being that when you point at one section of the image, another section changes.
You would need to create all the elements of your image, i.e. the four people and the background, and then right click on each and choose "insert slice" which will put a green box over each one. Then one each person, click the green box once, and a circle will apear in the cente of it. Drag this circle to the background slice and you will be asked to choose another image to use as the dijointed rollover. Repeat for other people, and that's it - just export to HTML and images and you're done! NB this is for Fireworks 4, Fireworks 3 is a little different. Use F12 to preview the effect.
Hope this helps!
Stuart