Short answers, pulled from the story.
A picture stone is an ornate slab of stone, usually limestone, raised in Germanic Iron Age or Viking Age Scandinavia. The greatest number are found on the island of Gotland, and more than four hundred are known today.
Picture stones were raised as memorial stones, though only rarely beside graves. Some were placed at bridges and along roads so that many people could see them.
Picture stones present their message primarily through images rather than runes. Some picture stones do carry runic inscriptions, but those inscriptions typically say little more than the name of the person to whom the stone was dedicated.
The three groups are dated 400-600, 500-700, and 700-1100. The earliest group has straight forms with vortex patterns; the second group consists of small stones with stylized patterns; the third group features tall bow-shaped stones with rich pictorial scenes including ships with checkered sails.
The largest picture stone on Gotland is found in Änge in Buttle. It stands 3.85 meters tall and is richly ornamented in the style of the 8th century.
Yes. A comparable tradition exists on the Isle of Man, where tall funeral crosses are carved with imagery of warriors and Norse deities similar to those on Gotlandic stones. Carved stone slabs in Scotland are known as Pictish stones and share a related tradition.