I created a github page and I have a custom domain for it. I used og meta tags in the head like:
<meta property="og:image" content="http://example.com/images/myfacebook.png"/>
Facebook debugger tool usualy returns response code 302, but on the fourth, fifth time it gets through with code 200, and recognizes everything fine. (don't know why)
But when I try to create a facebook ad here: https://www.facebook.com/ads/create/ my image never loads, I always get a small picture with a facebook camera icon. I know I could upload an image manually, but when I upload the png transparency turns to white. Anyway it should work, and it really annoys me.
I set up my domain records by the github pages help.