Found a treasure trove of royalty-free image, art, music, and audio that can be used freely (at least as of 12/17/2022 🙂
Image/Art
◆ photoAC https://www.photo-ac.com/
◆ illustAC https://www.ac-illust.com/
◆ silhuetteAC https://www.silhouette-ac.com/
◆ いらすとや https://www.irasutoya.com/
◆ GADGET STOCK https://simpc.jp/free/
◆ BEIZ images https://www.beiz.jp/
◆ Paper-co https://free-paper-texture.com/
◆ フリーテクスチャ素材館 https://free-texture.net/
◆ みんちりえ https://min-chi.material.jp/
◆ きまぐれアフター https://k-after.at.webry.info/
◆ ミヤタ屋（黒い仔山羊） https://booth.pm/ja/items/2383834
◆ KNT graphics http://kntgraphics.web.fc2.com/index….
◆ 佐藤真裸（midjourney） https://www.pixiv.net/users/42601023
◆ AIPICT https://aipict.com/
Audio/Music
◆ 魔王魂 https://maou.audio/
◆ HURT RECORD https://www.hurtrecord.com/
◆ audioAtelier http://audioatelier.jp/
◆ H/MIX GALLERY http://www.hmix.net/
◆ 音の園 http://oto-no-sono.com/
◆ Senses Circuit https://www.senses-circuit.com/
◆ DOVA-SYNDROME https://dova-s.jp/
◆ Re:I別館 145cmの考察 https://145.rei-yumesaki.net/
◆ VSQ https://vsq.co.jp/
◆ 効果音ラボ https://soundeffect-lab.info/
◆ Oto Logic https://otologic.jp/
◆ 無料効果音で遊ぼう！ https://taira-komori.jpn.org/index.html
◆ ノタの森 http://notanomori.net/
◆ 音人 https://on-jin.com/
◆ 騒音のない世界 https://soundcloud.com/baron1_3
◆ クラゲ工匠 http://www.kurage-kosho.info/index.html
Besides those, sign up here for a free royalty free photos
