You need a direct Link to a picture, I don't know how Facebook works,
where you store them and generate Links out of it.
I just took a Racoon from our local News Reel Site.
http://www.mz-web.de/image/view/2009/1/26/18176630,15832331,dmData,Waschb%25C3%25A4r+%25281235630266445%2529.jpg
.jpg at the end of the adress shows it's a direct Link to an image...
I would simply right klick the picture select show picture, copy the
cryptic code and add image post button to see if this works.
https://scontent-fra3-1.xx.fbcdn.net/hphotos-xta1/v/t1.0-9/11401027_113349599000396_5220306335947127782_n.jpg?oh=bbdc666e346b7f1bd0a771627c906dd1&oe=562B3534
If not, right klick and save the picture and use Add image to post to upload on postimage.org,
that way is fool proof, as such cryptic embeddings sometimes work here, sometimes not.
It works, just klick insert Image, that'll produce
[img][/img]
insert above cryptic code you generated from reight klick show image, voila
Hope this helps
Kind Regards
Tobias