There are some composition issues, I'm not sure I see them all clearly yet.

The clouds upper limit is tangent to the tree top, which is distracting because they already have not too dissimilar textures and tones.

The bg textures (both clouds and 'rock') have lines that 'go around' the center, which tends to make the eye wander aimlessly. Pointing those features towards the center might help.

The light is too even, both bg and fg. The typical idea would be to have a well-lit tree, darker ground level and darkest underground. Other options would be nice too: inverted, lightest in the middle, etc. The bg light gradient might be opposite to the fg's.

And maybe for a tree that's as unique as this, you'd expect wilder colors.

I think the composition could be more balanced.

On the left side, there's mostly verticals, and horizontals on the right.
Maybe just cutting the hedge fence would be enough.
But as Conceit says, don't add anything!

On top of the highest roof, the black line is unnecessary.

I agree too that Elk's edit is highly interesting.

Of course I can't judge how your face has changed since, but it also has better light and volume which should apply regardless of any change (they were there too in Helm's edit).

I'm aware these are really difficult to achieve anyway, but worth trying!

AAed the greyscale version (to a white bg; might need some fixing yet); tried more color versions (AA between color zones will have to be fixed).
I like messing with colors so much that I'll have a hard time settling for one. 

Hellaphone, DrD: