In some spots, your background dither lines up with the outlines, making them look thick and blocky. I think it might look better if you give the characters a small "halo" of a solid colour, to keep the dithering away from the lines.
In addition, it looks like your outlines have some random-looking gaps and jaggies, which I think warrant cleaning up a bit. The blue hair also has a lot of orphan pixels that look like noise rather than like highlights, I think a little clean-up would really help there.
Overall though, this is a really cute and well-drawn piece :D Are they random characters, or OCs of yours, or real people? If they're OCs, I'd love to see more of them :D
Lastly, your signature isn't full-opacity, which is generally a no-no on PJ.
Ahh wowow, thanks so much for the critque! I'll definitely work on fixing this piece in the areas you mentioned when I get the chance! And aha yeah these were just random characters.
Oh and thank you for the headsup about the signature!