It doesn't look like Pixiv has an API (as far as I can tell), so unfortunately we wouldn't be able to add it as an image provider to DisplayFusion.

However, if you set the Image Source to "My Computer" and clear the "Load random images" checkbox, you can use the Load From URL button to paste a URL from Pixiv in and have DisplayFusion grab the image. Not sure it that's what you're looking for, but figured I'd offer it as a workaround anyways

Thanks!