Are you talking about the background stuff or items or gui and not the characters, right?
I'm talking about The character sprites they are kinda too low res especially for small details, immor as a example I didn't even know he had pupils on his eyes until I actually looked at the character sprite, honestly character sprites should be double what they are,
and if you are worried about the size of the files just separate the parts of the sprites that are different from the base model and overlay them on top of the base sprite, a lot of vns use this trick, you will essentially reduce the file sizes by more than half and can have a higher resolution sprites in general