如果找不到图像，则显示某些图像的自定义图像 - Lighttpd

I have a site that creates images for some bit of content after the content is created. I'm trying to figure out what to do in between the time the content is created and the image is created. My thought is that I might be able to set a custom image to display on a 404 error on the original image. However, I'm not sure how to do this with lighttpd. Any ideas or alternatives?I have a site that creates images for some bit