Grey Moon
This first "moon" is simply a snowball painted black, then drybrushed with two shades of grey:
(Maybe I should have plucked off one more clump of flock, there...)
Terran Planet with Brown Moon
This brown moon is simply the same technique as the grey moon, but with brown shades. The planet was painted dark green, then oceans of blue and icecaps of white were added, and then everything was drybrushed white (representing clouds). The moon is on a "cut"-type base, while the planet is on a champagne-top base.
Slushball Planet
Here's an icy Neptune-type planet - or maybe it's a Terran waterworld. I painted it dark blue (though it ended up blotchy for some reason - which works well!), then drybrushed it with white (which can represent ice or clouds - or both).
Red Dwarf Sun
And here's the red planet I showed earlier, though I've decided it's a star and put it on the martini glass base.
Yes, the effect would be better if the star were actually glowing - but what do you expect for $2 USD? 