(a couple of thoughts too short for their own entries)
1) What if magic – which exists to break the established order of existence, with its laws of mass, of energy conservation, of logical and immutable causality – doesn't mutilate the normal user with its corruption, spellburns or madness so common as a consequence of multiple fumbles in various systems, but it is the other way around, and magic can only take ever seed in minds (and bodies) already dissonance and broken? In this case the normalcy is sterile ground: in order to get the magic, one's sane mind and healthy body must get damaged first.
It might explain why curses of people wronged and passions of people unhinged come true in magic while mundane desires of bourgeois in pastel shirts do not; why want-to-be-wizards go through fugue, it might explain drugs and other chemicals as a tools of temporarily going off-normal, or even fully insane.
But the risk here is that, while the magic is generally attracted to broken minds by its own blind, unthinkable nature, one never can be sure it would be specifically their mind the magic going to inhabit – there are no rules on whom the occult will seed, there is no way to force it, hence intentionally going mad might amount to nothing at the end if the magic, by the irrational nature of its own existence, simply doesn't take a hold. If one has a good and comfortable place in society already, and power over others that is more reliable and predictable than occult, intentionally going mad in scant hope to get occult powers is an open opportunity to end up destitute without any powers at all.
2) What if Conan the Barbarian but in cyberpunk? Mixing fantasy and mega-urban landscape is not a new idea but the appeal here in the known names reimagined: Stygian sorcerers as servants of abyss that are old Archeronian preserved minds which, in their turn, go back to forgotten Lemurian protocols.
3) What if museum instead of gardens? The memetic beast here, instead of thorns, would be a notion to enshrine the every moment of every being into a display – the sickness starts with note-taking, shifts to obsessive journallng, into replica constructions until the whole civilization is utterly paralyzed into nothing but putting everything that moves into clear archival resin and creating displays of themselves creating displays. At the end, the museum is full of treasures, both actual, and everyday mundane, and made from trash and it grows more distorted and grotesque as one progresses through the fall of civilization. The main actual treasure probably is finding eatable food and water in the place of replicas, and the end goal is probably not something grand and mysterious but just an exit, to tear themselves off eternity as the museum recording every moment of every creature would otherwise continues endlessly, similar to Library of Babel.