Higher contrast looks nice!

Yeah, biomes rather than features is a good way to think about it. You don't necessarily need a huge palette, though. For Earth you could easily get away with a couple of greens for different woodlands, and a few warm browns for sandy and rocky deserts and steppes, and a couple of cool browns for snowy mountainous areas. True-colour space photos (e.g. Earth as seen from the ISS) are really your best bet to see what you need! Water can generally be quite a solid dark blue (the shallow parts that would be a light blue tend to be small enough to be invisible at this scale), though eventually you'll probably want sunglint and/or an atmosphere, which will require some lighter blues.

If you're going to have terrain detail at all, you should think about the atmosphere first. No atmosphere is transparent. Earth's atmosphere is thin and transparent enough that you can see terrain through it, but a lot of detail is lost, and there are clouds to complicate matters. On Venus, it's always cloudy and though there is a rocky surface, you can't see it from space.

The atmosphere will reduce the amount of detail you can see to the major, large features. Deserts, wooded areas, snowy areas, etc will all show up, mostly melding softly into each other, even though in reality the transitions are closer to being stippled, the alternations don't show up at that scale. Dithering is appropriate to use since it's also basically stippling that looks like a smooth transition. Vertical features are usually too small relative to the size of the planet to be visible, so it's all about large-scale horizontal features. Even Mars's Valles Marineris has very little discernible depth when seen from space.

Think about the scale. How big does a feature have to be to be 1px wide? You drew beaches on some of the shores, but if that's an earth-line planet, then that means 1px of beach is over 100miles wide!

By the way, your game looks very dark. I have to squint to make out the details. Even the lander is hard to make out. Space, because there's no atmosphere getting in the way, can actually be quite bright, especially near planets that are close enough to stars to have what looks like liquid water.

Proportions are something best worked out before you get to pixel-level detail. Sketch or block in the body parts without worrying about making nice, smooth shapes or details like clothing, then add details and clean up afterwards. If you aren't sure what the proportions should be, there are plenty of proportion charts out there.

You dove into details too early, before taking the time to work out her proportions and pose. Also, if the 128x128 size is your working size and not a crop: I highly recommend working on a larger canvas than you need, so you don't find yourself squishing things in. It's easier to crop later than try to fight off the subconscious urge to distort things to fit.

Here are a couple of possibilities, one more realistic, one with anime/supermodel legs:

Like Hagane wrote, I made the crotch-heel distance equal to the head-heel distance. On a realistic person, the "crotch" position is higher, the anime legs have the "crotch" as being at the bottom, where the crotch ends. Note that it's the crotch-heel distance, meaning the distance to the heel of the foot, not of the whole leg. A character wearing high heels will have legs that look longer because of the way the foot is positioned. That's why the guidelines in my sketches don't reach the "floor".

The character's head is rather large, so the longer legs will probably feel more proportionate. The shorter legs would look better on a character with a more realistically-sized head.

Also notice how rough I made the sketch. This is because the goal is to just work out the proportions.

Could tooltips (title attributes) be added to the various icons, like "Popular Thread", "New post", etc? No set of icons can be self-explanatory to everyone, and on the web we have the luxury of tooltips to remedy that problem.