Yo.
This is a pretty cool idea.
Small rez is good to start out with and doing stuff on a regular basis does push you to be more motivated. Hope this small C+C adds to that motivation.
1
I'm seeing a lot of black outlines here. You can get this right, but at this size it's better to use clusters (shapes) of pixels to describe details (esp those buttons), outlines hog more space the smaller you work.
Shading is a problem here. You're shading the DS screen like a round thing (sphere) when it's flat (cube). I see this a lot in beginner art, not just pixels. But maybe the outline > flat color > shaded workflow encourages this in the digital/pixel mediums especially, because you're looking at that outline without thinking about the forms they describe. Basically you want to learn to shade these things by planes before you break the shading rules. Try out a few ball/cube/cone shading exercises.
2
This is probably another example of outlines over planes = small details over the big picture. The biggest drawback is on the curtain wrinkles, because it sort of drowns out the players in 1px details when they should be the focal point. Try thinking in planes (see #1) or blocks of color, this makes it easier to think about how the curtains get hit by light, if there's a spotlight there, etc., and it could make this way more interesting.
3
Probably the best one color-wise but I still wanna see less reliance on outlines, and a little more perspective on the buildings.
Going forward it's gonna be worth it IMO for you to rely less on outlines and absorb the ancient trade of correct 3D shading. Simple stuff that pays off in the long run.
HTH.