>>4152294Unfortunately seasonal images are not usually tagged as such on pixiv and the character for autumn (秋), 'Aki', is used in many shipgirl names so search isn't much help either.
Pixiv does have a few explicitly autumn tags (besides the Halloween ones) but they aren't as populated as they should be:
https://www.pixiv.net/en/tags/紅葉 艦これ/artworks?s_mode=s_tag (autumn leaves + kancolle)
https://www.pixiv.net/en/tags/食欲の秋 艦これ/artworks?s_mode=s_tag (autumn of appetite + kancolle)
https://www.pixiv.net/en/tags/秋の秋刀魚祭り/artworks (autumn saury festival - is more about saury than autumn, does not require kancolle tag)
For danbooru, use the tags autumn, autumn_leaves, and sweet_potato
For twitter, good luck.
