Is there a place that lists them, to include all of the hidden ones and how to unlock them? I've only been able to find information on the Morostide and Luminaire ones. Are there more?

there is only one more

I thought there was an article in the Wikia but can't find it, so no?

There are only 3 hidden ones, so if you know how to get all of the ones mentioned here then you're good.

Oh yeah, has a good point. Rouland and Devorah are tough opponents and so I was distracted that's my story and I'm sticking to it.

The official non-hidden ones are available through Forums - Options - Themes. There's a dropdown that'll show you the names of all the ordinary ones provided by Subeta. There is a fansite called Subetalodge that has some layouts created by them of their own that you could paste into your CSS.

I don't think there's a thread or site anywhere that shows you what they look like ahead of time so you will need to try each of them on to see if you like them.