Display a specific image from assets
You can do

 {% image = craft.assets.id(x).first() %}


Where x is the ID of your element. You can see the ids of your elements in your cp. There is a little wheel icon below your asset sources where you can define which attributes to display. Just check the selectbox for id

You can learn more about fetching entries with ElementCriteriaModels in the docs

Your problem was: you did not fetch the element. You prepared your database query but you need to execute it with first() or find() because