Ahhh, I see. Yeah, the texture is a bit blah, but that is why we have Paint! Paint fixes everything! There's "old school" cobble brick paint texture iirc.
Or you could just upgrade it to Concrete. Concrete fixes everything!
Or you could Concrete it THEN Paint it! Concrete and Paint fixes everything!
Just ask my ex landlord who tried using concrete as wall putty then paint over the suspicious black mold creeping down the corner from the ceiling.
Seriously though, If it can be an easy xml fix I'm sure someone here might help, but I don't see this being changed in game unless there are plans for a texture revamp.