Judith needs a background and I put this together very quickly to show how you can create one in Photoshop with Filter Render Clouds and Filter Render Lighting Effects.

Make a new layer beneath the image for which you want a background (Double click on your image to change it from a background layer to a normal layer, then click on the new layer icon while you hold the control key down and it will create a new layer underneath your subject.

Choose the two colors you want for your background. In this case I chose blue and white.

Go to Filter/Render Clouds and click on it. If the placement is okay leave it alone - if it's too busy you can crop it and enlarge it to fit the required area.

Go to Filter/Render Lighting and Choose Omni as the type of lighting and size and place the circle where you want to put the light behind your subject.

Make the top layer your active layer and see how it looks. Make any adjustments to your background layer after you switch to that as your active layer.

Make the subject your active layer and create a "floor" for your subject by using the burn took at lowered opacity - gradually adding shadows where necessary.