Not keen personally on the whole "just stick cogs on it" theme of VSF, but lots of Victorian Gothic features look appropriate anyway. Small railings on the roof, random turrets and towers (even in town centres) - and if they are square probably with railings on the top (look at the Adams Family house), possibly lightning conductors (easy to do but not very visual, unless you connect the bottom end to an exotic carriage charging device), exotic wind gauges might be a possible, or small semaphore/shutter signalling installations. I think Warbases did some of those for Napoleonic players. Window shutters might be an easy call, would look slightly exotic on UK walls.
Otherwise possibly go for odd shaped windows (Dr Strange house?). Quite a few MDF cutters have window frames on their catalogues. (Warbases also do them to order, I got some "Chinese" style ones for boxer/colonial buildings)