I think adding a partial outline to the eyes would improve readability better than just enlarging the whites. Like how Chuck has outlining under his eye. If they still look small after that, then enlarge them.
Any particular reason you're using a light grey as the base colour? The white present pretty much everywhere in the game would look a bit nicer. Also, the skin tone is rather yellow and pale. Some of the trainer battle sprites have healthy skin tones, you could consider using some of those for the different characters.
One last thing that I noticed was the small amount of dithering. It's kinda part of the style as long as you don't go overboard with it. All things considered, these look really nice and I hope to see more of your work!
EDIT: I checked your palette and noticed you had about 30 different blacks, and two nearly identical skin tones (sometimes on the same character, even)! Went ahead and fixed those for you in this link. The grey was also changed to the white used in the game.
Any particular reason you're using a light grey as the base colour? The white present pretty much everywhere in the game would look a bit nicer. Also, the skin tone is rather yellow and pale. Some of the trainer battle sprites have healthy skin tones, you could consider using some of those for the different characters.
One last thing that I noticed was the small amount of dithering. It's kinda part of the style as long as you don't go overboard with it. All things considered, these look really nice and I hope to see more of your work!
EDIT: I checked your palette and noticed you had about 30 different blacks, and two nearly identical skin tones (sometimes on the same character, even)! Went ahead and fixed those for you in this link. The grey was also changed to the white used in the game.