Obvious kneejerk is the highlighting and tidying up of any black elements, and the base.
Outside of this, however, is the consideration of any symbols (or other decoration) on the lower portion of the model.
The original ootb version of that mini (I forget his name) has the Inquisition symbol dead centre, split by the opening of the coat.
I did something similar for a xanathite with a symbol taken from The Secret World (Legends) TSW/SWL Dragon faction, split in the same way.
However, you could consider wrapping symbols around the hem of the coat instead, similar to one of the older 28mm eldar farseer minis, which had a section of hem on their inner robe specifically for that when painted as biel-tan (I've got a picture buried somewhere...).