My ideas, in no particular order.
Modrons are much more sleeker and simpler looking, and are chrome in colour. Mechanus itself is similar, being just a huge chrome factory. Primus controls Regulus through wires that link him to it.
The Yugoloths have formed a corporation known as Gehenna Industries. It basically is all the corrupt corporations in our world turned up to 11. Their workers go through the same hardships as the workers of Victorian times, having low pay and dangerous work.
The Plane of Vacuum is basically outer space. Citadel Exhalus has become a space station, black holes link the plane to the Negative, and inter-planer satellites are placed here because of the relative lack of obstructions.
The Psuedo-elemental Plane of Radiation. Negative Quasielemental is Gamma, and Positive Quasielemental is Radio.