Paint lol.
Why won't they work exactly? I just thought they were ugly. They seem workable.
your sprite's general drawing is fine it just has a few size issues
alas, compare your sprite with shell's:

to start off, your spritesheet isn't transparent. i can easily make your sprite transparent but it's good practice for the user to make it transparent themselves. microsoft paint doesn't support transparency, and that's a big thing. since your using windows, you should use
Paint.NET like alot of other pixel artists are using
next, notice how shell's character and wings are equally sized in blocks. looking closely at your character, you probably scaled it up and drew tiny pixels on it. you need equally sized pixels.