@Jellby -- did you check other offerings from internet archive? If not, I looked at these, and the images are darker/stronger. (Maybe too dark?) But it is always easier to go lighter--you cannot get back detail that is missing because the source is too pale and washed out the details. Anyway, you might take a peek.
https://archive.org/details/junglebook1899kipl
https://archive.org/details/junglebookkipl
https://archive.org/details/junglebook00kipluoft
Truly, there have been times I would have been thrilled to see a source as good as the one you have now.