Thule is a place somewhere in Scandinavia. Its exact location is a mystery, but many places assign Thule to Norway, Iceland, and even Greenland. Consequently a mixed up Scandinavian flag symbolizes this element. Thulium was discovered by a Swedish scientist, consequently its easy to see elements of the Swedish flag in the fun Thulium flag.
Since the atomic Z number is 69 the Yin and Yang atomic symbol is appropriate, it uses the colours of Greenland, which are white and red.