Hi there! Feel free to upload the stuff you have/find, just be sure to tag properly, and tag all cosplayers in photos.
Although there's no actual affiliation, the tagging should generally follow Danbooru's tagging unless exceptions make sense or are required. The general focus is stuff that would be rated General or Sensitive on Danbooru (so basically, no porn), though our ratings can be a bit less strict. It looks like you already got the gist of it though, so good luck.
