Panellus

The glowing mushroom has an interesting sort of hold upon the popular mushroom.  A natural phenomenon, bioluminescence has that sort of rarity and pageantry that renders is magical, luciferin-reactions-be-damned.  Be it known as will-o'-wisp, jack-o'-lantern, foxfire, or ignis fatuus, the natural lights of the night have always been portentous, heralds of good or ill, and spirits unto themselves.

The above is panellus stipticus, one of several score species of glowing mushroom known to man, in a rather wonderfully-patterned arrangement here.  Now, I need to set this pattern upon a man or woman - a simple enough task if used sparingly, for fear of creating a ruffles, glowing, green pinata instead of a tractable design; thus, the focus turns to accessories.  As an effect of such wonder and rarity, thoughts on such luminescent life turn to formal dress - a splash tie, perhaps?  No - an entire tie would overpower the ensemble in the dark, while it would pale in the light.  The next option is the pocket square - something which could easily be a simple color an pattern by day and light, and come to colored glow by night or shadow:

Within moderation, a tie, too, could work, if the glow is but a support to the body of the piece.  In the same vein, a sort of boa could serve as the same for the fairer sex, or provide an interesting touch to an elegant gown, detailed in places by black folds that later prove to be panellus plates.

The key here, as in the concept's origin, is surprise and rarity; that defines the boundary between an unbearable Day-Glo cacophony and a spirited twist.