I think the orchestration was a bit too simple at times, one major example that comes to mind is the fight scene with the multiple orcs. It really could have done with more oomph and a musically fatter orchestration. I just felt like there was too much open air in the music to be the emphasis of a battle scene.
I really missed hearing any recurring motives. There may have been some, but none were memorable enough for lightbulbs to go off in my head. It seemed like perhaps you were trying to be a bit too Howard-Shore esque and lost sight of it? Forty minutes is plenty long enough to develop and few motifs.
Overall I really commend you on many things. The general audio mix was great, the choice of when to have and when not to have music was spot on, the general mood created by the music was fitting, the instrumentation of most of the cues was appropriate, it all fit the vibe and time period of the movie.
One last thing I'll critique is that some of the devices you use to achieve certain moods are a bit cliche(ie. the high strings during pause moments of the orc battle scene). You can get away with them, but its the little creative nuances you put in that really distinguish your music from say, Howard Shore's. I'm not saying get rid of the high strings, I'm more saying embellish upon them somehow to make them unique and fit into the musical entity as a whole.
Overall, it was a good movie, although the best actors were the orcs :P You're music certainly got the job done though, you're well on your way.