Start by clicking Layer > New fill layer > pattern and selecting the default wood pattern. Create a new empty layer and merge the two layers so that there is one layer that contains only the pattern, that is directly editable.
To make the wood appear more realistic use the Burn tool, select a soft brush to darken the edges. You can also use the Dodge tool and again with a soft brush on a low exposure setting gently make the centre of the wood brighter.
To add a final level of realism use the Dodge tool on a high exposure and lighten a one pixel border around the edge of the image. Finally using the Dodge tool on a ‘Spatter’ brush, enlarge the brush and start to gently add a ‘scratched’ effect to the centre of the wood. Use this brush on a lower exposure around the edges to make the wood more realistic.
Once you have finished you can add some objects such as a coffee mug.