Playing Sounds
I'm sure folks have even more information, but here are some basics I have found:
Amazon has an extensive set of sounds available for Alexa.
[Alexa Skills Kit Sound Library | Alexa Skills Kit]
This can be played easily with the proper string into a speak() command
<audio src="soundbank://soundlibrary/sports/crowds/crowds_12"/>
can be sent to a speak command, to play the crowds_12 sound
Note: ES devices have a command playSoundByName(), that has a more limited set of sounds to choose from. You will have a larger set of sounds by using speak() commands with strings like above and should have access to the full Alexa library listed above.