No tribe put "art" on their tipis, since that word is used to describe purely decorative painting or drawing.Medicine lodges and the lodges of important warriors or chiefs were painted with designs that had either sacred and spiritual significance or indicated the war deeds of the warrior who lived there, so it was far more than simply art.Very few Lakota Sioux tipis were painted in this way - most were left plain. Some had other forms of embelishment, such as the medicine lodge of Slow Bull, which had small locks of hair sewn to the cover.See links below for images: