I had some time to fix it
- change the page size to a fitting power of 2 size and fit the object into it.
- don't stop the rope diffuse light at the ends.
- use correct diffuse lighting on the columns and changed the other ones.
- removed duplicated diffuse light filter effects.
- removed duplicated columns and cloned the bottom left one. (same with the planks)
- other small things
It's not yet upstream so you can still change it.