Y'know, my first and (admittedly) so far only Pred head sculpt was something almost identical to that. So I will respond to this one as several others responded to mine (much to my chagrin): : "AW, IT'S CUTE!"
Seriously though, that's pretty good. I'm no expert of course, but everyone says to start small, so you're on the right track.
Hi Fireblade, that's not bad. All the basic shapes that make up the pred are there. What it needs now is some refining. What is it made from? The modelling material you are using may limit the amount of detail you can acheive. As for your question, it's probably more difficult and fiddley adding detail to a smaller piece, but as you go larger you have more detail to add so it's swings and round-a-bouts really.