I saw an interesting coat of arms on a building just the other day and wondered if I could waymark it.
Lots of municipalities have their own coats of arms. I've noticed this particulaly for towns in Finland (hello to Small Oaks by the way), who often display the coat of arms on their municipal web pages.
There's plenty to think about here ....
An (slightly silly) extreme example, in the UK the organisation of registered gas installers, CORGI, has a logo of a shield with the word CORGI on it. Now, that's clearly not a "coat of arms", so waymarking the offices of gas installers would not be wanted, but coming up with the rules could be quite tricky.
Similarly the Harley-Davidson trademark of a shield with the words "Motor Cycles" and a bar with the word "Harley Davidson" doesn't seem to fit in with the spirit of the category, so waymarking motor cycle dealers would be out.
On the other hand you can't disallow all commercial marks, because many will be in the language of heraldry and may have historic roots. Coats-of-arms were probably (??) early forms of trademarks.
(Thinks ... maybe disallow shields with writing on them, as opposed to heraldic symbols)
What sort of waymarks do you want? Permanent outdoor displays?