Links with blix

K ‘im french so excuse me for mi bad english.

So i’m using the blix theme by Sebastian Schmieg for doing mine personalized theme.
seen there: https://ntrivalle.free.fr/wp/

I would like to create link with pictures like we can did by the admin editor. But the picture doesn’t appear. How can i change this. Is it a wordpress or a blix theme problem ?

Thanks for all
Blink.