This is how a wall might look after seven centuries of exposure to environmental impact:
Originally, it would have looked like the wall on the left side here: this is the courtyard side of the same castle, after and before renovation.
And both are details of 14th-century Château de Saumur in the Loire Valley:
Here is a collection of all kinds of typical wall decoratoins of 13th an d14th cenutry French architecture, at Château de Blois:
My particular favourite is the porcupine as heraldic animal.
The indoor wall decorations of the period weren't that bad either: details of a tapestry depicting hunting scenes... some happy dogs! :o)