The moon and planet aren't at all bad, but the sparkles seem a bit poor--it's the same ones repeated too much and they're not all that visually interesting anyway. I'd try and mix them up a bit and give it more of a flow to the sparkles--certainly vary their angle and size more at least.

Also, although this is a space scene there doesn't appear to be any stars. Now although technically for proper photography that is accurate (due to the brightness of the planets) it's kinda become such a convention in art to have starfields in things like this it seems wrong when they aren't there.

It's also quite easy to do a basic starfield--you can use the noise filter and there are tutorials out there to help you get it looking right.