SNAP YAPB

Hello,
Using SNAP to do auto posts to the Facebook Page and using YABP to just post 1 image per Post No Text etc.
Now I wanted to use SNAP to ‘Post as Image‘ to the Facebook Page for that I need to declare “Featured Image” , From Where I do that ? any plugin to define custom field “featured” and then just put the URL of the uploaded YAPB image for that post so it gets the featured image ? because uploading the same image twice will be bad pratcie

Any workaround for this will be appreciated
Thanks

SNAP: http://wordpress.org/extend/plugins/social-networks-auto-poster-facebook-twitter-g/

YAPB: http://wordpress.org/extend/plugins/yet-another-photoblog/