(Sorry English is not my first language, so I might phrase things a bit off here and there.)
I think the character art is really good already, to me it looks like it was hand drawn on paper, which I think looks pretty cool, and it gives the VN a unique look. I also like the different lighting colors for each character (Maxewell - red, Eddie - blue, etc.), it gives them a certain mood. The one thing I would say is that the character art clashes with the current background images. I think even raw, black and white sketches would be enough as backgrounds, it would blend much better, and the characters would stand out even more.
(I personally do not think detailed background images add much to a VN, and often it might do more "harm" than good.)