Almost all higher end Nikon cameras have Multiple Exposure functionality in-built. I used Nikon D7000 to get the below image.
Enable multiple exposure and take two different exposure, your camera will overlay these images for you. I took picture of myself with white background, and second image was of palm trees. Used Photoshop to get rid of unwanted palm trees from white background.
And here is the result.... Don't worry, if you have entry level Nikon DSLR, you can still achieve this, using Overlay function. Little effort is needed. check this out Multiple Exposure hack in Nikon D3100