Only because they're from the same place, doesn't mean they're compatible.
Your character sprites have a lovely simplified, painterly style, complete with outline.
The rest is your usual fare of extremely detailed pixel sprites.
Painterly is not compatible with pixel per pixel detail.
Painterly looks organic and natural, the pixels flow to make soft transitions of tone within the colours.
The other sprites are extremely sharp, each pixel standing by itself to bring out the most detail.
I hope this makes sense now.
Edit: Actually here is another comparison;
Lets say the painterly characters are like cel-shaded sprites.
The non-character sprites boast so much detail they're pseudo-realistic.
Cel-shaded sprites on top of pseudo-realism doesn't fit as they're of totally different aesthetic directions.
Your character sprites have a lovely simplified, painterly style, complete with outline.
The rest is your usual fare of extremely detailed pixel sprites.
Painterly is not compatible with pixel per pixel detail.
Painterly looks organic and natural, the pixels flow to make soft transitions of tone within the colours.
The other sprites are extremely sharp, each pixel standing by itself to bring out the most detail.
I hope this makes sense now.
Edit: Actually here is another comparison;
Lets say the painterly characters are like cel-shaded sprites.
The non-character sprites boast so much detail they're pseudo-realistic.
Cel-shaded sprites on top of pseudo-realism doesn't fit as they're of totally different aesthetic directions.