A little background on the San Damiano crucifix. It has great significance for the Franciscan Order, and even for the whole Church, as being the image from which Our Lord spoke to Saint Francis, telling him to "rebuild my Church, which as you can see, is falling into ruin." Francis, being the humble, simple fellow that he was, thought that the Lord was referring to the little chapel, so he began begging for stones to make the repairs. Of course, the Lord was speaking prophetically, that Francis was to rebuild the Church through his friars, sisters, and layfolk.
Some strange things about the missal, though. One is that it really isn't even a San Damiano crucifix. Here is the original, now hanging in the Basilica of Santa Chiara in Assisi:
So what is the one on the cover? Beats me.
And yes, the San Damiano is an icon of the Risen Christ. There's certainly nothing wrong with that, and any Franciscan would recognize the image and be proud of it. Remember, St. Francis was the first saint to receive the Sacred Stigmata, so he was no Assisi sissy. But why is it on an SSPX publication, where most people probably would not know its history?