I snuck into the Temple of Dibella to steal the statue. They noticed me right away and started attacking, so my follower killed them all. From what I read, I thought they were going to ask me for help and I wasn't intending on killing them all.
Anyways, I'm at a point in the game (level 60) where I don't care as much about ruining a later quest...from what I read, the only reward from the quest you otherwise get from them is a permanent Dibella blessing.
I could reload but I get tired of that...so I'm wondering if there might be other things I ruined by killing all of them.

You ruined the game by killing the sixiest chick in the game (Senna).

Since Senna was in the entryway (and not in the lked room), she was the only one who was not killed :-p

I think there were marriage options downstairs and you won't get Agent of Dibella.

That quest is required for Master-level Enchanting training.

LOL. So true!!

How is she sixy? you can't barely see her face with the hood on?

Besides, Hroki (spelling) who hangs out in the Markarth market area is way sixier. At least her clothing is anyway.

She has a pretty face and since all the bodies are the same if you've ever stripped down a dead, female, hostile NPC you know what you're getting.

Also, she says flirty things - I assume she continues to say them (and maybe more) if you marry her.

Required for Master level enchanter training? Then the quest is irrelevant. It's so easy to get 100 Enchanting.

if you are on pc you can add Senna to follower faction and remove/exchange her stuff. She is exotically hot, with white hair, pale skin, pale blue eyes, and an oddly attractive face tattoo. Wish they would have used a different lip color though....