For suggesting images for pages Facebook uses linter, you can check yourself what's wrong with your page (for some reason no images are visible for Luxemburg at all - try to purge TYPO3 cache and lint again):
Best you can do is to install or create some extension which will help you with creating og tags it's good concept especially if you want to make your page co-working with FB on the longer run.
Edit: Weird, after closer look I think that's facebook's problem not TYPO3's, change a way of link creation, i.e. remove/comment config.baseURL
from your TypoScript and add this in your TS (Setup) instead (don't forget to flush whole cache):
config.absRefPrefix = /