Plato's Ion is essentially all about creative inspiration. There are quite a few comparisons used, but his central argument is a metaphor. He says that like a magnet attracts iron rings and then imbues them with the power to attract other rings, so too a muse inspires the poet, who then inspires the rhapsode, who then communicates this effect to the final ring, the audience. This is all part of his argument against there being a τεχνη (art/craft) of poetry, but that it all comes from the muses.

He also says that the poets are possessed (literally "gripped" in the Greek) by the muse when inspired, such as the Bachants, worked up into a frenzy, which is why they cannot explain how they compose as they compose.

My personal favorite metaphor was that they collect the drippings of milk and honey from the garden and glades of the muses and then bear it back from that realm for the rest of us.

I realize this is only Athens, but I just finished translating Ion, so I thought it might be of interest.

"Inspiration" is a concept going back at least as far as some very old books of the Hebrew Bible - it's a major theme (and an obstacle to translation) for Ecclesiastes, which constantly draws on imagery surrounding the Hebrew word ruach, which translates very nicely into the Greek pneuma. Both of those mean "wind" or "air that moves," and they both also have the meaning of "motivating force" or "the thing that animates living bodies."

This is literally a force that creates - ruach is what God moves across the waters to create the land, and what he breathes into Adam's body to create humanity.

That said, I don't thiiiiink ruach (or pneuma) would have very much to do with getting an idea. That's still usually something that's described in terms of "light," or, like the burning bush, or the light that guides out of the pit in Job, or maybe the fiery figures that appear to Ezekiel. Those are all guiding lights, so... well, maybe flashes of inspiration, maybe not.

(Probably important concept: in the ancient world, "genius" was something that more often than not lived outside you... it was a spirit that you interacted with, not something that came from within. It possessed you, not the other way around. So when Moses sees a bush, or Ezekiel sees burning figures or hears his "still, small voice"... this reflects a different understanding of psychology and a different concept of the self. I'm sliding between Greek and Hebrew again there, but I think it's valid in this case.)

In Ecclesiastes, knowledge is painful, so light is more about happiness, although it's also used as a kind of what-God-knows symbol (everything "under the sun" as opposed to the dark places where the dead go that God knows not), and at least once lightens up a face.

"Spark" is used as a metaphor for inspiration in English (as in, "That sparked off an idea".)

Apparently, it has only been used as meaning stimulate or trigger since 1912, however.

http://www.etymonline.com/index.php?allowed_in_frame=0&search=spark&searchmode=none

The light bulb was invented around 1879, so this term does not pre-date the lightbulb.