ToME: the Tales of Maj'Eyal

I bought the shimmer packs from the website (te4.org), downloaded each of them and put them in my addons folder. I checked in-game, they are listed as Active in the addons section.

So far so good.

I load up my character, try to change his item appearance in the mirror...but there are no extra shimmer options.

Do I have to make a new character now that the shimmer packs are installed? Am I using the wrong thing; is there something else that uses the shimmer packs I'm unaware of?

I'm very frustrated...

Any help would be appreciated!

New addons don't apply to existing characters. Changing the addons a save file was using can break them, so it won't load any that weren't active when the character was created.
The game does list which addons are active for each save file.

Ah yes, when you install the packs using the ingame options, there is code to force the addons to enable for yoru character, but when you do it manually well, there cant be :/
What you can try is remove the files you installed, then use the char you want to enable them on, go to the MTX interface select Use and select the packs and if the ingame browser is enabled it should work.
If this doesnt work, it's possible to edit some files in the save to force it, but it's a bit trickier