Hey there, welcome to the forums!
These are good starts for a beginner :] Not much here to critique. Your "characters" could use a bit more contrast; the dark mood is nice, but they blend in a little too much to the background color.
Keep pixeling! You've started nice and small which is good, now do something more ambitious so you can mess up more! That's how we grow. Perhaps try a full mockup with background and ui.