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You should post the signature into your post then just to clarify that you have 4 sprites to showcase.
Well first of all, you've saved several of your sprites in JPEG. That Pikachu is looking a bit flat so i suggest shading it, though it may be too late with the JPG fragments. The Pikachu still has loads of problems despite being saved in JPEG. It's outline is very choppy and not very clean, you've done a good job with it's left ear but it's right ear should look similiar to it's left. The tail's lineart is very decent though i think it could be better.
As for your second sprite (the person), the three shades of purple for his hair are very close, i just suggest to make it a little bit more darker, the jacket looks like to have some simple shading, though there are a better ways to shade it. I think you might be having two light sources for him, the top left corner and the top middle.
Your overall progress is great, you just need to remember to save your works in PNG and clean up your lineart. I suggest looking up a tutorial, so i took liberty on giving you onethat i did not make.
I'd move this to the Pixel art/ Sprite showcase, but you'd just be reposting your work, since you tried to make a thread like this in the Pixel Art sub fourm. If you're going to post Pixel art, go to the right section; which is right here on this link. Please remember, when you're posting a galllery, have 4 examples of your work. I'm going to lock this up since I can't move this to a thread he already posted this in, and this couldn't be a gallery, even if I move this. =P