If you're making changes then can I suggest one other? I ran some pages through the Facebook debugger and the only error message that I got was that
meta property="fb:app_id" content="xxxxxxxxxxx"

was missing, so I edited the plugin so that I could enter this in the plugin settings and have it included. This is not a serious omission, but I was trying to eliminate all FB error messages.

Sure, I can add that.

Reminds me, I need to make some changes in mine. I made my own plugin out of html_meta_tags.php to keep updates from wiping out my changes to it. I modified the code to use my normal image for the og:image.

Sometime in the future we probably will provide a filter so you can modify the output without customizing the plugin itself.

i have some questions:

• what is the FB app id ?
• what the use of Open graph image - height / width ?

The Facebook app id is a means for Facebook to identify your site for metrics. Similar to the Google site verification id (which I will incorporate into html_meta_tags as well).

Open Graph allows setting a size, that's it for. Social networks have recommendation for the size that change constantly. So you can never match all but you can at least set the lowest common denomator size here. The size is uncropped as the networks do what they think anyway…

googleVerify is a core plugin. You will incorporate it into html_meta_tags?

btw, I am not sure:
for `and
var caches = [...] the cache url for the image is never used and stays with the/zp-core/i.php?a=album_name&i=image_name&[...]` structure.

googleVerify is a core plugin. You will incorporate it into html_meta_tags?

Yes, as I wrote above. Does not make sense to have a separate plugin for just one meta item.

I have to look at that cache urls. Actually it should be used only once as always unless you cache the page before it is cached. If you look into the source of our site (album or image page) you see it is the cached url. That js for the uncached urls is rather a workaround anyway…