Botanical Graffiti

Consider that idealized graffiti is a statement of art, as art, and as protest. A bad graffiti artist (you know who you are, Mr. Single-Black-Lines-and-Can't-Spell) should not denude the genus of expression any more than a bad poet makes you burn your anthology of Yeats. If someone tells you otherwise, laugh pointedly at their error. Cities are made ugly. Graffiti just makes that ugliness human.
In this capacity, we arrive at a new problem with guerilla gardening/seedbombing/botanical graffiti/et al., which is "Can it look good on its own merits and still serve its purpose?" To answer which, yes, it may. Anyone can plant a damn clover. In fact, clovers do a pretty good job of that themselves. The real power of this medium is similar to Buddhist protest; how can the power elite fight an ideological battle against a foe who is in favor or freedom and life? How can you go to war against very, very nice?
In the XTC song, "River of Orchids", we hear mention that, "the grass is always greener when it bursts up through concrete." This statement, while beautiful and incontrovertibly true, is also a subtle admonition of botanical graffiti. Really, what planted anywhere in the urban moonscape doesn't look good by comparison? I've seen withered chicories awkwardly stretching like a beginner's yoga class, up from between grates and beneath trash cans. No person cast those seeds. For a "seedbombing" to be successful, it must be surprising, yes, but irony cannot and must not be the final word of this Weltanschauung. It must also be a vision of the wonder of which it is a part, the antithesis of what it rejects.
But it will start small, like all good gardens should.
I had a sudden inspiration, regarding beautiful seed paper, after reading the previously posted moss tags recipe. This prepared nutrient goop would seem to provide a better than adequate growing medium/adhesive paste for a variably-scaled poster project, involving different plant species (and thus, differently-sized seeds), unto which the sheets could be further decorated, drawn, or written upon before finally being swallowed up in vegetation.
Also, as I reflected upon it, I do not think solid clay is the ideal means of preparing seedbombs. Clay, though absorbent, does not hold water especially well unless it is kept in moist conditions. And it doesn't contain a valuable mix of healthful elements which a sprout would appreciate. I think a potting mix or peat moss base with a clay mix to stabilize the shape for its short life as a ballistic statement would be best but until I can do a field trial, myself, I won't stand behind that innovation. Perhaps someone else has experimented with it, already.
The moss paste itself makes me think of perpetrating giant Chia pets. And of creating signatures which unveil themselves slowly across the brick facia of old buildings. I suggest brick for moss, since moss grows best in poor to no drainage. Soaked brick would dry, of course, but I think it would release water very slowly if properly saturated, after the fashion of a garden pot. A timber surface also would suffice, though the moss's growth would deteriorate the material unless it was pressure-treated, in which case I think it wouldn't sprout at all.