I think implementing this as a standard feature wouldn't go along with the stackexchange answer design, which is text-oriented. If you start adding such pictograms, you'll have to allow for others, which might well trigger an avalanche of such graphic elements.
However, what bars you from just inserting the picture in your posts manually? In order to avoid uploading it every single time, you could save the snippet somewhere on your computer (some even like to use their info box for that purpose), and then you copy and paste it.
As long as you don't overdo it on the signs, I say go ahead. I've seen Paulo Cereda and Frank Mittelbach using such elements in the past and it looked nice to me. I'd probably be careful about editing them into other users' answers, though.