Hello @Atlasmuseum, thanks for your message! Hm, I'm not entirely sure. Personally I'm not a big fan of the notable work (P800) property because it's so extremely subjective. When is a work 'notable', and why, and according to whom? If you add the property for all works and creators on Atlasmuseum, why shouldn't I add it for all works and creators on all the other websites I'm using to add public art to Wikidata (for instance vanderkrogt.net and bkor.nl which I use all the time, but I'm not associated with these sites)? Do you see my point?
That said, any other 'hard' data you add about the artworks is absolutely very welcome (items for the artworks themselves, creators, dates, coordinates etc). It's indeed very much preferred that you use the artworks' own web pages as references there. It's a pity that there is no freedom of panorama in France... it would be so nice to be able to add images to modern and contemporary works.
Please keep up the good work and feel free to ask anything.