Any suggestions for the composition?

I love birds. We don't see enough of them in renders. How about adding some tiny little other thing on the tree, like a bug, just to contrast the beauty of the birds?

 Okay on the bugs - but it is winter... I'll look at adding old leaves from the mountain ash tree - 
The gray waxwings have yelllow and some dark feathers -
The berries will have more texture - and less perfect looking.
The snow will be rougher on the berries and branches - 

Hope this is of some help.
Some of the colours seem a bit strong for me.
I feel there is no particular "point of entry" for the eye into the image or a circularity of eye flow which takes you around the imagerey and back to the entrance point. (Does that make sense?)
Part of this is contributed to by the similarity of size of the objects but also by the llimited variations in the objects colour differences?
Red/yellow  colours always looks as though they are at the front, so things that are further away should be less red/yellow?
Having been that critical, your drawing/modelling is, really ,very good.

I prefer the original length to width ratio as it has a more "oriental" feel, which suits the bird and bush dual theme.
The good item to keep from the second picture is the cast shadow of the one bird on the other. As this is a chittering chattering flock, it is good to have the shadows interacting also!
The interaction of the red sunset with the red of the figures is exciting, should be fun to paint.

they look like some kind of african finch.
let us know how the painting turns out, omin.
around here, the waxwings eat pyracanthus (sp?) and toyon berries in the rainy season.