It's no surprise that advertisements/branded locos are a part and parcel of IR now. What is the weirdest branding you have seen? Mine was roaming the empty LJN platforms with with only the Shatabdi standing and the PA system started branching off ads about a Paan Masala for OVER AN HOUR on loop.
Quite ironic since those paan masalas are one of the major things that destroy the visual appeal of the roads/rails/anything that comes in mind.