From my point of view, the one required accompaniment to a terrine of foie gras is some good country bread, grilled if possible. After that, I often like to pair foie gras terrine with a sweat compote or jam, such as a fig jam, poached quince or apple or even dates. Because foie gras is often paired (successfully!) with Sauternes, I find that the flavors I associate with that wine (honey, vanilla, pear, spice, etc) tend to pair well with foie gras as well. I also find that almonds and walnuts work well as a pairing, so I often use a toasted nut bread. In the photo you mentioned, I believe that we were serving our terrine with almonds sauteed in olive oil with sea salt and also apples poached with Coteaux de Layon, a sweet wine from the Loire Valley.