A trick for sky banding is to use layers of clouds.
You may specifically not want clouds but if you want to try, just refer to what I did with your other piece here
http://www.wayofthepixel.net/index.php?topic=15481.0I'm not great with these so I did this as an experiment.
I was going more for a sunrise there (i.e. its been a long night of zombie killing) with dull colours, but in your sunset you would probably want some more vibrant and intense colours.
The sexiest sunsets I've seen have hues of orange and pink (especially on cloud highlights), blended into either light or dark blue.
Sometimes there's some yellows in there too.
Also keep in mind what I said in that other thread about composition, explained better here
http://en.wikipedia.org/wiki/Rule_of_thirdsYou can go for centered subject matter if you really intend to use a symetrical composition to your advantage, otherwise it is likely to look nooby and unnatural.
Lets say your theme is balance, well there are other ways to create balance.
For example something large NEAR the middle, and something smaller further to the side - imagine the subjects on a jigsaw, not by their physical weight but by their visual weight (size, contrast with surroundings etc).
In this case the guy could be meditating nearby some carefuly stacked round boulders for example, which again is communicating theme of balance.
According to what light is coming from the background, you can add a touch of rim lighting around the meditator.
If part of the actual sun is showing, try bleeding the light into the dark spaces a bit as happens in real life.
You could use 2 or 3 layers of hills in the background, which is a good opportunity to use athmospheric perspective to create depth and add to the sunset mood.
Simple smooth curves with solid fill colour and gentle anti-aliasing (do this at the end) will give a good, calming effect.
You could even attempt to arrange them such that it resembles a sine wave...
I would keep them fairly low in the composition (say not too much higher than the bottom third gridline) or it will detract from the sense of height of the meditator.
Wherever possible, recycle colours you already have and keep track of your palette.
Don't stress too hard over this though.
If you feel a recycled colour doesn't fit or you intend to use colour to change a dynamic, then its a good time to add a colour or ramp to your palette.
When you are ready, try making a few variations of the same image and just play with the palette.
Your piece could even be the same image 4 times with different palettes...
EDIT: Just stumbled across this sunset while drooling over Vierbit's portfolio *wipes mouth*: