CD... you seem to have no clue what you're talking about...
The tutorial by MarvinX doesn't concentrate very much on creating the actual texture. It's a very simplistic method in fact. And regardless of using background or skybox technique, the images must still be made. And that's what this thread is about...
I'll post something considering my experiments on the subject later today. But as a tip: using plasma, colorize and brightness/contrast you can create continents from the bright areas of plasma cloud and thencoulour the continents gray/light brown. Then use freehand selection to choose which areas are forest, which are mountains etc. If you want, create valleys and stuff onto mountain areas, and perhaps some rivers onto mainlands.
If you want to avoid exessive spoilage around poles, simply put ice caps or open sea there. They are the easiest way to avoid ugly thingsies from forming on the pole.
Besides, I don't think it would even be good to always use similar method to create planet texture. It would result in massive amounts of generic planets, something I personally am against. Different kinds of methods create variety.
Though, creating gas giant textures is easy compared to earth-like planets or plain barren rocks. Just create a background layer of arbitrary colour, then put one or two cloud layers on top of it. IWarp works well in creating belts and zones on cloud layer, just slowly move mouse vertically, clicking occasionally. Then move to other zone, change the direction of swirl and move to other direction, still clicking. Cover the whole planet like this. Shadow layer goes on top. This creates a nice, Jupiter'esque planets; other gas giants in Solar system are much less detailed. Saturn has rings, but Uranus is just a blue blob and neptune is not much better. The other one of them has some white storms on them, but that's it. They look dull... and that makes it more difficult to make them look interesting.
One more thing that is easier with gas giants. Atmospheric effect is so thin that it's usually not noticeable, because the planets themselves are so frakkin huge that the width of atmosperic effect would be about <1/1000 of the planet's apparent diameter, so it's just not visible. They are just sharp edged spheres or ellipsoids, making them much easier to create. I might do some gas giants next...