(By nice I mean compatible as best I can with the latest ePub specs, images SVG traced for hi-dpi / dark mode compatibility, attempts to best meet the original layout choices, full endnotes etc etc. Only thing I wasn’t able to do that was on my list was a generative marbled page. Maybe I’ll come back to that at some point.)
Marbling was a relatively new technique at the time, and each copy had a different version as they were done by hand rather than printed. It’s there as a reference point for the preceding page, quoted:
You will no more be able to penetrate the moral of the next marbled page (motly emblem of my work!) than the world with all its sagacity has been able to unravel the many opinions, transactions, and truths which still lie mystically hid under the dark veil of the black one.
It would be nice to write an algorithm to randomly generate them. Ebooks are extremely limited in the randomness aspect, but potentially I might be able to hack the SE toolkit to supply a seed every time the book is built.