There is an ad campaign in London at the moment for Portuguese tourism. You can see 48-,24- and 16-sheet adverts in the tube with giant portraits of famous Portuguese celebrities (Cristiano Ronaldo, José Mourinho) with a landscape showing through the image. Something similar to this effect that can be achieved with only a few clicks in Photoshop.
It helps to find a picture, like the one below of José Mourinho, that is lit from the side so half the face is white and the other half black. However, failing that, find a portrait that has a white background. Once the image is chosen, cmd/ctrl-click on either the red, blue or green channel in the Channels palette. This will give you a selection.
Now find your “background” image and paste it over your portrait image. Now click on the New Layer icon in the Layers palette to give you a blank new layer. With the selection still live, fill this layer with white. To do this either go Edit > Fill… and in the resulting pop-up box chose White for your fill (the quick key for this pop-up box is shift-F5) or simply go cmd/ctrl-delete to fill the selection with the background colour (the default background colour is white; to get the default foreground and background colours, simply press D). You knew that!
You may want to copy this white layer (cmd/ctrl-J) or alter it’s opacity.
This is a simple and effective way of putting one image inside another with interesting and eye-catching results.