I have seen the following trains having kannada boards: Ernad express (MAQ-NCJ), Parasuram express (MAQ-NCJ), Intercity express (MAQ-CBE). The MAQ-Chennai egmore express has only tamil and english written probably due to the fact that it belongs to SR and traverses a good distance in TN and probabky has got RSA with some other Tn based train .
If i am not mistaken Maveli express and Malabar express do have boards written in Kannada. At least in a couple of coaches i have seen it.What abt Santragachi-Mangalore. I guess it would have Bengali since it belongs to South eastern railways.