How to attach video and sounds to web pushes?
At the moment all web browsers do not support this kind of features. When such support from the developers will be introduced, we will follow-up shortly.
To be more specific, there are no plans we heard of from leading browsers like Chrome and Safari to support push videos anytime soon.
Speaking of custom sounds, Chrome seems to be developing in this direction by implementing a few parameters for supporting this feature in the future but it is not defined at the moment and due to this seeing no actual use.
Here's a quite good breakdown of web push customization possibilities from Google documentation for your convenience.