some critique, eventho this is not a c&c thing i suppose.
im not a good writer so i'll keep it short.

there's an issue i'd like to point out about looped, inverted frames. at the moment the movement of the breating animation looks more like a jellyfish swimming in water because of the same frames used in inverted timing. there's no real fallout on the clothes nor hair, you should pay attention to where they are draped, where they get their initial movement and the varying weight of the objects.
i guess you can go around with the magic wind explanation. im not familiar with the world that the character is in thus making it look unnatural in my eyes.
the breasts look like they want to follow the direction of the body moving, but at faster pace. like the breasts are trying to compete which will be faster at the end with the body. there are several different styles you can use to make them look bouncy, firm, natural, simplest propably being a 1 frame delay on the boobs compared to the chest. then you gotta think about the gravity forcing the breasts to move more downward and harder from them to move upward. in a small sprite like this i think a 1 pixel difference between chest and breasts is enough. now they look like they could hit her in the head all the time. i wouldnt' want to breath while being scared i might get hit in the chin with my boobies if i was her.

about the palette, im not going in specifics but by using a palette such as the one on games factory is very limited and simple. this usually makes the sprites have very generic choice of colors aswell. blue, red, green. if i remember correctly there were some links or tutorials on color in pixelopolis. and of course the net is full of them, some of them bad, some of the worse, few great.

just brought up few things that came to mind. not neccessarily right:)

edit (positivity included): the tutorial is good, having the basic info you need to start animating and has good points. i just didn't agree on some of the methods you used. and it's a nice looking sprite, but everything can be tweaked to make them look better!

-tomi

love the mockup, really nice colors on the samurai but i agree with madafacka on the ninja tho.
your current ninja lacks depth (especially on the shoulder) and detail (headclothes). you should see pics of real ninjas how their clothes were assembled, they're wicked cool too =) now the head looks like it's more of a robot ninja than a human ninja.
the samurais front arm could benefit from being less bulgy, maybe use more dark shades on the bottom pixels and on the hand to stand out since it will be in mobiles i presume?
also add roundish shadow on the samurai to make it look less like flat plane (straight line on the bottom).

the basic rule to make foreground stand from background is use darker more contrasted shades on the foreground. and that you have achieved

-tomi