The setup misses everything that you could do to let me experience his work in a setting reflecting his time.

An Italian Renaissance palazzo, the house of a nobleman of that time, maybe Leonardo's re-imagined studio etc.

Instead I see a museum that one of my architect friends might get excited (or offended) about but which completely removes all context from the works that the format you choose would otherwise naturally enable.

On that note: getting the colors of the paintings right is also tricky.

When you source these paintings you need to feed their color to a linearization process (as they likely will be in some non-linear color space like sRGB) before applying any scene lighting. And then finally do the display transform. Otherwise horrible things will happen (do happen in your current setup) to the colors and Leonardo will turn once in his grave every time someone opens the website. ;)

Thank you for the feedback. The later stops are his last house in Amboise which we rebuilt. For the earlier stops we decided on a building to serve the walk as well as possible. On colors: we decoded the images from sRGB, but the color filter over the scene and the video change them a bit on the wall. We will look into it. The close view shows them unchanged.