I've been composing for all genres of music since I became a professional in 1985, including writing albums of production or "library music". Quite often, (don't hesitate, directors), pieces of library music will get used in TV programmes (see here), or films (far too numerous to mention!). Oh, and Spongebob Squarepants loves my stuff....ahem.
But even when you're NOT commissioned for the job, and your music gets used, well it's a pleasant surprise (or shock).