Not ideas really, but imagination.
Where can your mind wonder, and what can it bring back for your piece?
Without imagination all pieces of art would be repetitive.
Imagine yourself in a world where all colors are black,white, and grey. Then all of the sudden, a blue color emerges. Imagine the joy, and thoughts that would go through the peoples head? Would it set off ideas of other colors?
If one person can be creative, and let their imagination wonder, and make a piece with what they have seen, then others can learn from it, and teach themselves to imagine too. It sets off a chain reaction of sorts in other artists heads.
I guess this would be included in "Ideas" But I think Imagination is the most important part of ideas.