Sprite Ideas

Tone down the saturation/brightness on the yellow for Cyclops's gloves and shirt there. Also, note that you didn't color the yellow for his "walking forward" sprite on the left. For his blinking sprite, just don't change anything from his static shot, there's no reason why a character with his eyes covered should have a twitching face in his blinking pose.

I would actually make the blue on Nightcrawler a little more pale. You can't see any of the detail of his face with such a dark color of blue, and it makes him look really weird. The bright red could also be less vivid, but that's not a big issue.

Also, for both of them, on their "arms raised profile" sprites, you completely left Locke's Bandana and Gau's Ponytail on the sprite. Need to at least get rid of those to have an acceptable sprite.

It's not a bad start. You need to practice more, of course, but you're on the right track.

Keep working with these. Try changing Locke's Jacket into something more like one of Cyclops' actual costumes. (Again, try to avoid using such vivid colors, though, or at least make sure that the rest of the palette is just as vivid. Locke's hair and skin are too pale for the bright yellow and red you used.)

Think of these as your 'practice sheets', and keep tweaking them until you have something you like. For now, try just changing the jacket on Locke, we'll eventually work towards changing his hair and giving Nightcrawler a proper tail and his trademark feet. And then we'll move onto more advanced techniques like shading and proportioning.