Some of these look totally ridiculous and like they couldn't possibly exist, so here are some reference shots along with the planets:
Hubble photograph of Mercury
Image of Venus from universetoday.com
And they Tiny Planets they inspired:
Apparently I like doing brightly colored gas giants, but then I got into moons and Plutonian bodies.
Got a little silly with colors:
I'm still doing them, but at this point, there are way too many to show here!