Its a good first draught, but there are a few things which stand out to me:
1. There is no little grey margin to the RIGHT as there is on the LEFT.
2. The header has lots of empty space. Try and fill the black in with something.
3. Its very grey, which isn't too bad by itself, but all the extra colours you introduce are in the header. You need to distribute/repeat them throughout the design or else your colour theme will be unevenly distributed and look bad.
There... that should keep you busy forra while!
