If you're planning on making a vocalsynth video and need some art for your character, did you know you can use art from Piapro for your videos, as long as you credit?
https://piapro.jp/
The same applies to art in the UTAU and CeVIO 支援中 Pixiv tags!
https://www.pixiv.net/en/tags/UTAU支援中
https://www.pixiv.net/en/tags/CeVIO支援中
I'd like to add on to this if that's okay! Crediting is important, but also, looking at the terms of use for any image is important as well! Using Google Translate can help for reading them!
Also, the material image tag on piapro is useful for finding a background image!
https://piapro.jp/illust/?categoryId=5