Thanks for that Jehannum, will definitely have a read!
Dotodrymo, yeah I know the piece is quite mixed in regards to lighting and the mood I'm trying to set. Like I mentioned earlier I'm just testing out and getting a feel for things.
As for the tree being straight, I was trying to recreate a style I saw from one of my old nintendo games haha

I like the dithering style used. Speaking of which, after some googling I found a poster showing different styles you can use to achieve certain textures so I gave that shot and took your advice with the lighting. Although I'm still having trouble with the back (darker end of the tree) just can't seem to visualize how the shadows would wrap around.. once I get the technique down I'll fix up the colour palette.
Let me know what you think of this revision:

Thanks again guys, appreciate all the help!