What do you want this Founder's portrait art to look like? Please list the physical description, Action & Magic, Clothing, Accessories, and Background that you would like to see for Mercere's portrait.
I think there may actually already be a portrait of Mercere in HoH:TL; at least, there's a full length pencil drawing of a man with a Redcap and ridiculous moustache in the "Mercere the Founder" section on pg 79.
A man rides a horse down a medieval road. It's snowing, and clearly has been for some time; few people would be out in such weather by choice. He wears a red cap with the symbol of House Mercere on it (upside down triangle in a circle), and a cloak that seems strangely dry and clear of snow. He looks broadly consistent with the existing picture of Mercere, but perhaps a bit older.
His horse bears saddlebags. One of them is bulging and securely closed, but strapped to the side of it are two pieces of a broken staff. The other one has the head of a white cat poking out of a gap between the flap and the side of the bag.