NOTE#1: When using a file://-based TiddlyWiki please note that the usual Browser sandbox restrictions for accessing (media) files apply. You cannot access files outside the (download) sandbox.
NOTE#2: As it has been the same-origin policy for ages, you cannot access YouTube videos from a TiddlyWiki -- unless you get it uploaded on Google's servers ;)
NOTE#3: Due to the same-origin restriction of loading (not only media) resources, the plugin has an enhanced TW5 server that needs to be used instead of the stock TW5 server when creating TiddlyWikis via a TW5 server on node.js.