Before I give much critique, I’ll point out that I was planning to model his head at one point and there is a huge abundance of good reference images, including the one you posted at much higher resolutions.
http://freecelebritygraphics.com/images/celebs/hugh%20laurie/house-8058.jpg for example.
If you have heaps of reference already then feel free to ignore, but if you go to images.google.com or whatever and select images over 2mp in size (in advanced search now I think) then you will start to get much better results for a current celebrity/actor like Hugh Laurie. Press photos and such.
As for critique, the main thing that jumps at me is the back of his skull. The face itself is a good start, especially seeing as you haven’t done this sort of thing before. It seems that the rest of his skull seems rather shrunken. Bringing the forehead out, making the skull taller and bringing it back out a bit at the back of his head would help overall proportions I think.
As for texturing, have you uv unwrapped the mesh? You will need to at some point, and if sculpting you will need to do one of two things. Unwrap the lowest level of the sculpt, or sculpt away and then use the retopology tools to ‘trace’ a new mesh over the top. Then unwrap that one.
http://www.blendercookie.com/2011/01/21/intro_uvmapping/ - help on uv unwrapping if you don’t know what that is yet.
http://bendansie.com/BD_BlenderHumans.pdf - long pdf tutorial on texturing a human face for realism using photos. A bit outdated and perhaps long winded, but I wrote it so I’m allowed to say so…
http://vimeo.com/3485932 - video version of the previous tutorial method. If that helps you more than a written tutorial. I’ve been meaning to update them a bit, but its a priorities thing. More fun stuff to do.
Looking forward to seeing this progress. Also looks like you are (relatively) new to the forums, so welcome if noone has said so yet, hope you enjoy your time here!