Blorp dev here. I’m copying the thumbnail url into the post url, but perhaps that’s incorrect. I’m open to suggestions. Again, not confident I’m handling this correctly, but one advantage of setting post.url is cross posts are compared via url, so setting that url would allow Lemmy to associate cross posts of the same image.

On the rendering side, Blorp scans post.url and if it’s an image (e.g. ends in .png), it renders it as an image post. But perhaps not all clients do that.