Yes, you can get a "plain" black cloak in WoW.

[Weatherwax]

If you're GM of your guild, or can convince your GM to do so, you can get a plain black (or any color) cloak.
You just choose the most unobtrusive motif for your guild cloak and color everything black.
It's how my guild does it. We chose black because it's so easy to coordinate with anything else.
You can also do the same to your guild tabard. It makes for some interesting xmog.

[Holdodlig]

Or you can farm this one :
https://www.wowhead.com/item=166671/...=1537#comments

[betonstahl]

maybe put a Z for Zorro on it?