On the first two, you should dither to give the picture shape and volume, and not only for using less colors.
I'd say you could first color the pictures in blocks of colors (giving volume, shadows etc)  and once you have planned all, just start dithering if so.
(The face could have the cheek bones and lips and other wrinkles the skin makes more pronounced for spicing it up for example)
But well I remember seeing that dragon in pixelation it has improved since then.

As for the rest, The CD icon looks pretty nice, the green foggy houses is ok, maybe a tad boring composition wise, but not bad for 2 colors.
The chibi demon you, IMO has a bad palette choice, at points looks pillow shaded and in overall somehow looks jaggy (and without trying to offend) somehow disturbing for the eye, at least to me.
The card, somehow looks forced. The objects look just pasted there and forced to go together, and somehow dont "click well", but the detail of not just mirroring but showing the other side of the jack is nice.
The animated dude looks nice, but the choice of palette doesnt do it for me again.
And last, Yoda, looks pretty nice, though somehow doesnt share much similarities to the movie one, but well pixelled.

Keep pixelling, and good luck with new stuff.

First of all, what I think you are in need of, is some kind of reference to base you pixels on, since it doesnt really look like a sword.
IMO what is going wrong here aint nor AA nor dithering, but just a matter of composition and wrong palette usage
Here is one, fastly googled: http://www.northlandgifts.com/images/items/VA54100A.jpg
Now stare at the ref., and squint your eyes to simplify the shadows, and pixel and shade the sword as what you see.
Dont pixel from the top of your head if you arent really sure of what you are doing.
Use a reference to base on and as said before, pixel what you see, and not what you think it might look like.
And same with the palette, pick it according to what you see, similar tones to what you see.
Not trying to sound harsh, but you might want to consider repixelling the whole thing rather than just editing.

Just my 2 cents, and hoping to see more updates.
Good luck

I think that the shape of the mouth sets it off making it not look like a panda.
Maybe the addition of a nose could help, but I believe that that kind of mouths only work on er... let's say "animals" with small snouts.
Might be a matter of style but doesnt convince me at all.
I just noticed that while you put some blue light source on the left (our left, and so making the hair blue/purple) it doesnt affect the arms nor legs on any but on the one holding the broom, so yeah you might want to check that.
Maybe the shadow that the hair makes could be AA'd better, but ah well.

Other than that, adorable.
Keep the "panda<3lvoe" coming
haha sorry XD

oh and pixelation? i went there and it wouldnt work! does someone know the link? maybe my link is wrong...

I think he pretty much meant THESE boards :0

Really nice, as I told you a few times already.

But again, as said, though I understand what you told me about it, the big hand still bugs me.
You, kind of, dragged the focus away from the jaggedness on those things on the big guy's head using that blue highlight.
Couldnt it also be applied on the hand?

Anyway, just that.
Impatient to see the other pieces