stargood: i had that sometimes over the years. It is just an image display issue, and has no effect on the game itself (aside from that you cannot see how many pieces are stacked up).

If you go to another computer/smartphone, the problem is typically gone; you might be able to resolve it by flushing your buffers (use CTRL + F5 on a PC), or purging the cache (depending on your browser).
It could also be that the image server currently has an issue with this file.

P.S. I can also see your pinned pieces.