for exemple, dragon ball z, can i tag picollo as "namekian" or vegeta "saiyan" or these anime terminologies are unfitted to be tags?

I don't see why such tags wouldn't be acceptable.

"What is a Namekian?"
Do you understand what I'm asking? Tags aren't typically based on insider knowledge. Posts are simply tagged to describe the picture and info that you might find from a character list of each series' episodes. So...
"What is a Namekian?"

Keep tags simple: "Green, antenna, pointed_ears...etc."

"Who is Goku?" wouldn't that question also be "insider knowledge"? I mean there are many people in the world that haven't watched Dragon Ball...they couldn't tell Goku from Vegeta from Kirllin if their life depended on it. So using that standard you've basically said that all character tags are invalid...unless the character is literally announcing themselves in the drawing "I am Goku!" because that would no longer be outside information.

A better way of looking at it is TWYS (Tag What You See). If you see Goku, and presumably know who he is, you can tag him because he exists in the drawing. If you see a Namekian, and know what that is, same thing...you can tag it. Doesn't matter if many people don't know what a Namekian is, that's irrelevant, because many many people don't know about certain obscure characters, but that doesn't mean you shouldn't tag those characters.

The issue you run into is with races like saiyans because without their tails (and most in the series at this point don't have their tails) they are basically just extremely muscular humans with spiky hair. Or the character Android 18, who for all intents and purposes looks exactly like a normal human female, but is actually an android (same with Yorha 2B). In those cases...I really don't know what to do, but I don't think it's appropriate to tag them with "saiyan" or "android" because visually they are so indistinct from a human. But Namekians are extremely distinct so there should be zero issues with tagging them.

My answer is no.
If another mod allows the tag, then I will too. Otherwise, tag what you find from the post ir info as detailed as IMDB(which is minimal garanteed).

Lol...since when are tags based on IMDB? Tags are a tool for people to reach what they want to see. If certain people wish to see a specific thing like namekians then why stop them? Seems like you're imposing your poor understanding of tags on everyone else.

You realize that if we can't tag fantasy races then the "draenai" tag would also be invalid, right? Are you going to remove that tag? Same with many other specific Warcraft races...night elves, blood elves, tauren, etc.

Also...take this as an example...what if I was to draw an unnamed namekian babe. My own creation. She wouldn't have a canonical name. The closest thing I could do to naming her would be to tag her race, but you're saying I shouldn't do that...why?

Descriptive terms that are official and accurate should be fine, obviously if it's not clear from the image what they are, just as it might not be clear what kind of animal for example and we have animal types as tags, care needs to be taken on what to tag them as if it is not clear.

But I see no reason not to allow things like what type a character is, we want people searching to see a Saiyan to find one.

Thanks for answer guys