I kinda wanna watch Fate/Zero nowFollow

Surprised you didn't know about the Fate series before.

I guess there are a few things you should know about Fate/Zero. First, it is a good show and probably worth your time to watch. Second, it is the prequel to a very mediocre show--Fate/Stay Night. Third, there is a heaping helping of a context and events surrounding both shows that you won't be aware of because you don't know anything about the source materiel. Fourth, the Nasusverse is strange and hilarious on its own account. For example, that character was originally a dude.

I rather enjoyed Fate/Stay Night. And that image needs to be a wall scroll, though I'm not sure I need a third Saber wall scroll.

You might want to ask Nick about that, as he knows more about FS than I do.

I think any background reading would inevitably lead to spoilers, and oddly FS/N and F/Z provide mutual spoilers for each other.

It's not really that complicated or important of a story, and both anime series are written to be watched as stand-alones. I'd suggest FS/N first and then follow it up with F/Z, as F/Z is the better series and your appreciation will be helped by the context and adn comparison of FS/N.

If you were to watch F/Z first, then FS/N would just disappoint.