Bears have grown to become very popular in tattoo art recently due to their broad and rich use in symbolism throughout history and culture. Around 500 BC, the bear was used by the Celts across Europe as a symbol to represent war. In the Old Testament, this magnificent creature was used to symbolize evil influence and cruelty. In Christian symbolism, they were viewed as a positive representation of reform. In Ancient Greek and Egypt, it was believed that the Great She-Bear of the Ursa Major Constellation (The Big Dipper) was the incarnation of the great Goddess Diana or Artemis.
Bears have also been used extensively in Native American culture. For some tribes, they were used to symbolize battle, hunting, and healing. For other tribes, this symbol denoted the whirlwind which was used in times of war to confuse ones enemies and for medical and healing purposes. Some tribes viewed them as supernatural creatures and some even as Gods. Their annual hibernation was an expression of the need for silence and self reflection. The quiet of the cave was a symbol of the quiet of the heart.
Another reason why these tattoos have such diverse meanings and designs is the diversity amongst these creatures themselves. Bears such as the Kodiak and Grizzly can be used to symbolize immense strength, power, and danger. Polar bears in tattoo designs are rare and unique. With the current crisis this species is facing, a design incorporating this bear might be used to signify the last of a dying breed, to create awareness, or to symbolize hope. Other members of this family include Black bears and Pandas.
For anyone considering a design with a Koala, just remember that a Koala is not really a bear but actually a member of the marsupials. Finally, there are "teddy bear" tattoos which symbolizes "cute" I think.