I have a few tips that have not been covered yet
JankyTunes tips
Regarding sound, a few times people have mentioned my JankyTunes contraption, which hopefully should have enough documentation on how to use it already contained within, but people have asked if/how it can be used to play during a Dialogizer sequence. It is possible! There is some details on this in the "Advanced Features" section of its own doco but I will try to explain in less terse terms here.
Essentially, the way Dialogizer allows other scripts to run while it's doing its thing is by each frame calling an "animate[]" function that we can define on the card or deck level. You may be familiar with this if you've used Puppeteer in conjunction with Dialogizer, as its setup process requires putting such a function in place.
We can use this same functionality to get JankyTunes playing while Dialogizer runs. JankyTunes has its own animate function, designed to be called once a frame when there's something blocking the usual function. Basically the same as Puppeteer's "animate" function that's called in the Puppeteer setup process.
So basically, you can put something like this in the code section for a card with a jankytunes widget on it, and it'll not only be puppeteering but also jankytunesing!
on animate do pt.animate[deck] jankytunes1.animate[] end
You can also take advantage of this same function to have a card playing music from a jankytunes on a different card - i.e. so you can have continuous music playing across multiple cards. I wrote a bit about this in the jankytunes blog, in this post! You could even use these two techniques together - just changing the jankytunes reference in the on animate to refer to which card the widget is on so it's like "card1.widgets.jankytunes1.animate[]"
Getting jankytunes to play through a card transition however is not something I have a solution for though, so if you have like a fade between two cards the music pausing while this happens might be unavailable. I think for a lot of VN-type things you may want like a "tune per location" thing so having one jankytune on each card playing a relevant location tune while the characters puppeteer around and dialogueise at each other might be a good way to do it.
Looping multiple sound clips
But JankyTunes is not the only way to break the ten-second barrier of Decker music. Decker does have the ability to play a sound on loop - but it also lets you override the loop handler, which means with a bit of coding you could have it cycle through a series of sounds. I did something like this in my Asteroid Run game, which you can grab the unlocked deck to take a look at. But a simple version is just having a hidden slider to use as a counter, and then every time the counter increments playing a different sound. Although, I've found it works best if you separate each clip on the beat or between bars, since the loop is not always seamless.
Tips for sound importing
One thing with Decker's audio is that it is SUPER crunchy. Basically it's 8khz, 8bit mono. 8khz means basically that it's super muffled, so high-frequency sounds basically aren't there. And 8bit means that there's not much dynamic range, so things can get pretty fuzzy/noisy sounding if it's not at max volume. So if you're creating sounds for Decker it helps to take this into account - I've found that recording with more normal settings and then using Audacity to boost up the volume and compress the dynamic range a bit can help things import in nicely. Another thing to note is that audio sounds pretty different between native-Decker and web-Decker - they each handle the interpolating up to your computer's more normal 48khz 16-bit differently so it has a different sound, and the timing in native-Decker is not as tight as in web-Decker (this is why jankytunes often sounds out of time in native decker). Since we're releasing stuff on the web in itch, it's worth checking how the sounds sound in web-Decker to make sure it's what you want.
Puppeteer lip flap tips
One great Puppeteer feature is that in conjunction with Dialogizer, if you have Dialogizer set to have text appear one word at a time, you can have Puppeteer animate the lips along with the text appearing. This is pretty well covered in the doco for the two modules, but a challenge I had at first was figuring out what a good lip flap animation was. Until fellow deckmaker ahmwma told me about the Phoenix Wright trick, which is basically an animation sequence of "closed mouth -> open mouth -> half open mouth -> open mouth -> closed mouth". It's pretty effective, and I've used it in a few of my games. So maybe that'll come in handy for you.