Some very good ideas so far.
Back during the Iraq war some buddies of mine started noticing new graffiti all over the city walls. So they contacted me about it and I told em that terrorist cells and dissident groups and Saddam's old RG survivors were likely using it as means to communicate positions, operations, etc. It was made to look like ghetto graffiti which is often just gang-graffiti describing basically the same things anyway, on a different scale. Of course that's been going on in cities since the Romans and before, but people keep forgetting it too.
So we made a study of it as a code/crypt and eventually cracked it, and I understand it was used against them.
I think that graffiti like that would work very well in a city adventure, especially if you had dissident groups, revolutionaries, agents of espionage, criminal cartels and gangs, etc active in certain areas of the city.
In some active underground areas that might work well too. Coded, cryptic graffiti.
Someone suggested graffiti enviable except to certain frequencies of perception. I think that an excellent idea.
Another idea that occurred to me are glyphs and glyphing traps disguised as graffiti or glyphs painted over with graffiti as traps. Or to trigger certain events or situations, or even to mislead or misdirect.
A third idea would be "floating graffiti." If you touch an object in a room then floating graffiti might appear in the air, maybe even with verbal components. If certain images or symbols keep re-appearing then they might trigger certain events, or what they represent might become eventually apparent. Or it could be a floating code. Or key to a code.
A fourth thing that could be done is to place mapping elements within the graffiti images so that if you study it carefully enough you might realize it is a coded map. Perhaps with real and valuable information, or misleading information.
You could also have shifting graffiti. Suppose the adventurers stumble into a maze filled with graffiti. They think the graffiti is a way to naturally account for where they have already been (we've already seen those exact images). But as they move through it perhaps the graffiti is part of the maze and it shifts and changes form every time they encounter it, so that they think they are using the graffiti to map their location, when in actuality it shifts making the maze that much more difficult to escape.
Perhaps there are magical graffiti monsters that take shape out of the graffiti images.
And time-graffiti, or magic graffiti. Graffiti that changes over periods of time, is magically designed to do so, or graffiti that changes, alters or only exposes itself in the presence of magic or a magical item, or near a miracle (such as a clerical spell).
You could do a lot with graffiti. Very good thread idea BG. Unfortunately I cannot give out more XP today.
I blew my XP wad already.
