Manga Spoilers in the Anime

[Munsu]

Yuki, no you can't make sigs of any character. For example, you couldn't make sigs about Kimimaro until he was shown in the anime. And the mere existance of a character model can be considered a spoiler, but let's not go off-topic.

It's a very gray area, but that's the way it is.

So nest, I would say it's fine to use them, since they are already shown in the anime. Just don't reveal their name nor anything that hasn't been shown in the anime yet.