All the small things
The light bulb is an obvious choice when the theme is "ideas" but I tried to use it in an interesting way... I liked throwing in a few random objects as well, but most of them are handy ideas or inventions. The little ideas make up the big picture, or something like that!
The glow-in-the-dark ink was a little extra I added at the end, I think it's a bit of fun but the design doesn't RELY on it.