First highlight the face using the lasso tool, when the ants are running round the face only, create a new layer, still with these ants running round the shape of the face go to filter, change your colour pallet to brown and black. Go to filter>render>fibers, play with the variance and strength and you should have something that looks like wood grain. still on the layer play with the layer properties and opacity to find a successful combination. You can then add various brush textures to create a distressed textured face! These can be downloaded just search the web