I have just deployed a new image proxy for lewd.sx, written in crystal. It's open-source and available here. This is the first part of lewd.sx to be written in crystal (yay!)
If you see any image errors, you can open the image in a new tab and get a descriptive error message of why the request failed. Usually, it will be because the original URL went missing and is no longer returning an image. If you are sure the original image URL is valid, reply to this thread with the proxy.lewd.sx URL and I'll debug it for you.