Arms and legs, while not exactly common, are part of European heraldry. They are used on various coats of arms of families or towns. I know that the city of Fuessen, Germany’s coat of arms is actually three bent legs in a circle. In Europe, many times if a prominent family donates the money for building a certain aspect of a church, they will often visibly display their own coat of arms in some fashion. Sometimes this will be in an abstract way like only displaying an arm or a leg which represents the primary symbol on the crest. For example, you see stylized stacked hills and bees everywhere in Roman Churches because they were the symbols of the dei Monti and Barbarini families who were major patrons of the Churches
There also was a historical trend at one point in German liturgical furniture to use body parts as structural elements. Generally, this can be interpreted as saying that the Scriptures move in the world under their own power. It was a typical concept which was usually used by the Protestant Reformation in their defense of Sola Scriptura, but the Catholic Church also used these elements to simply symbolize that the Scriptures are alive with the Holy Spirit and through them, they move the hearts and minds of men.
As to the hands, it could also be the coat of arms of the Franciscans which is Christ’s outstretched hand and arm laid across the arm and hand of St. Francis of Assissi, both palms showing the wounds of the passion.
I find it hard to imagine.