Both appear to be signed "J Servais 92".
My Google-fu may be weak today, but I've totally failed to find any reference to anyone called Servais in connection with the Zilverpand centre. But they are striking works of art.
I have a hesitant identification of the artist. The Belgian comics artist Jean-Claude Servais normally signs his name in capitals, and also normally adds an emphatic C for Claude, but even so I think his signature looks similar to those on the Zilverpand paintings. (Singatures taken from various hand-drawn art found in online auctions.)
Jean-Claude Servais' usual style is admittedly more naturalistic than the escalator painting. Out of curiosity I got and read his 1984 album, Isabelle, which is the most popular of his books available on Kindle. The second frame of the third page is Isabelle, the title character, greeting her doll:
The troubador who loves Isabelle fortunately sings in lower case:
So we can do a more direct comparison of the writing, particularly since the word "serais" is conveniently in the first line of that frame, and "erv" in "épervier" a bit lower down:
Well, you can choose to believe it or not, but I'm reasonably convinced that this is the same handwriting, making allowances for the different flourishes you make when writing out a song or when signing an artwork.
Isabelle is beautifully illustrated, but I found the plot a bit less compelling - she and her lover are, er, very young; both are swept away to the Land Of Scantily Clad Fairies, where the Fairy Queen becomes jealous of Isabelle and brings about her doom. Still, I might try some of his later work.