Ideas...
 

How could I possibly make this better?

Personally, I think it shows a lack of depth. A bad perspective...hmm.

The detailing is too..blocky and pixelated..

You didn't explain this too well...

Basicly, your tree looks like there is an invisible line in the center of it. The truck appears as if you're above it, but the pine part of the tree makes it look like you're under it.

The reason this line seems to appear is because the rest of the branches have a long area in which they spread, and the middle branches spread quickly, in a seemingly unnatural way.

This tree isn't very good from a realism point of view, but if you're going for a cartoony, or fairytale feel than you've got it. It's chunkier than a real tree would be, and short :P

Thanks you. ^^ Thats excatly what I was going for.

How about don't be a lazy dolt and lay off mirroring your images. It's bloody obvious you only drew half the tree, then flipped it. Not only that, you can tell you tried resizing it. It's obvious with some of the pixel shapes. Never use the resize tool with pixel art. Seriously.

:whatever:
:frown:

I have to agree with Scott. The image lost 50% of it's quality when you mirrored the treetop.

The line where you copy and pasted one side looks retarded.

You can try adding a bit more variation on the oppsite side of your tree, as Scott sugested. You may also wish to use colors that have a bit more contrast, as it stands they are a tad bleak. However, before you do any thing, I would sugest you invest some time into learning more about pixelation, it appears to be the style you're using, and the more you know about it, the better the results you will get from your efforts. You can find a lot of good tutorials about pixelation at http://www.zoggles.co.uk/asp/tutorials.asp?show=index

Thanks. :)