If your having trouble thinking of stuff just do something like this,
Just take like a stock photo of anything and change something.
Here is like an example of a bad manip I did ages ago.
Stock:http://i154.photobucket.com/albums/s...3562Medium.jpg
Product: http://i154.photobucket.com/albums/s...tsdarkcopy.jpg

its very basic but will still help you.