This is how it is.
I also belong to the website ROBOTECH which is a site for the fans of the anime series from the 80's.

There is a section for Fanart and I placed artwork of the Robotech characters up there. Now I'd like to put them up on THIS site, but I wondered if it was permitted.

For one thing at least that artwork was also non-profit.

Me Emjar

Weee-eeell... The copyright stuff isn't a problem since that's for you to deal with, but there is an issue about using a comic account as an art gallery.

We don't really support that.

... but, if we don't notice then you could get away with it

Fan art galleries attached to your comic are fine.

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Robotech is officially AWESOME.