I wrote a tutorial which explains how to change/add a background to a photo here: http://www.golivewire.com/forums/peer-sisoes-support-a.html
Background Removal
In this step, you will learn how to use the
lasso tool to remove the background of an image. If you have just opened your image, it might be called 'Background' in the layers palette. If so, double click on the layer and click Ok. This will allow you to easily replace the background of your image later. If you cannot see the layers palette, go to the Window menu and ensure 'Layers' is ticked. Select the lasso tool. Roughly select a part of the background by drawing a line around some of it. You might need to zoom in (using the zoom slider in the top right corner - if you can't see it, ensure the 'Navigator' is ticked in the Window menu) if you want a more precise result. Hold shift while selecting more of the background. This will add whatever you are currently selecting to what you have already selected. Holding alt will allow you to remove parts of the selection.
When you have selected all of the background, right click on the selection and choose 'feather'. Feathering your selection helps to smooth any jagged edges and gradually blend your selection into your new background. Experiment with different values of feathering, probably between 2 and 10 pixels depending on the size of your image.
Once you've done that, hit the 'Delete' or 'Del' key on your keyboard. Viola! Background removed. You can add a new background by opening another image, then dragging the image using the
Move tool into the one you just removed the background from. Your new background will appear as a layer above your original image in the layers palette. Click on that layer and drag it below your original image to apply it as a background.

Post edited at 8:14 am on June 7, 2008 by Brookie Chookie23
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