The character of Leah Strade is a nod to Inspector Lestrade, from the Sherlock Holmes universe. Numerous other Sherlock Holmes references can be found in The InTEXTigator series, including Leah's Diary ID (2218) resembling Holmes' famous 221 B address, and the sub-titles of the films of the series, each a reference to the titles of Sherlock Holmes novels.
Marija Petrauskiene, the Lithuanian artist based in the UK, was actually modeled after Julija Lapeña, the actress who played her. The Director had met her online when he was casting for a previous film.
The premise of the stolen painting was inspired by the Mona Lisa heist in 1911. The heist was one of the reasons that made Da Vinci's painting famous, further highlighting that multiple factors can lead to an artwork's true value, as is mentioned in the film.
2 of the art pieces ('The Silent Witness' and 'Ocean Waves') used in the film were custom made for the story. The rest of the pieces were already present on location, and were painted by Denys Golemenkov of the Gol Den Gallery.