When it comes to the shapes of a tribal tattoo, they can be separated into the 3 classifications for which they were intended initially. These three classifications include that of religious or elemental, social status and then camouflage.
In the religious and elemental classification, these are all symbols that are focused on religious beliefs. One thing to remember is that non-Christian societies believed in natural elements as a form of religious expression rather than that of a depiction of a crucifix and God. This classification can include things like religion, form almost any religion in the world except for Christians since their beliefs dictate that tattooing is a form of bodily mutilation and therefore a sin. You will see various tribal symbols like those that represent the 4 elements of Earth including wind, water, light and fire. The concept of fire is actual dictated by the sun and it is therefore seen in many tribal tattoo art forms the sun being depicted even though the meaning of the tattoo is fire. This can be seen in every one of the elementals depending on the tribe for which the tattoo was used in.
Then you have the social status tribal tattoos, these can include things like animals and plants which dictate a persons status in society based on their tribes natural beliefs. For example, a person who has a tribal tattoo of an eagle would constitute being higher in society than that of someone with a tattoo of a raven. But then once again, the ability to define the difference actually comes down to the individual tribe’s beliefs. One tribe may place the eagle as high in society, while another may dictate it being high in military. Furthermore, the raven may be considered lower in society or even considered to be evil. It all comes down to the tribal beliefs.
The final tribal tattoo is probably the most common especially during the Paleolithic era in which the body would be tattooed similar to that of animals as a means of camouflage. These could be as simple as lines to hide the hunter in the grass, or even as complex as to tell a tale of a great hunt from the past. It is not uncommon to find tribal lines depicting that of a great hunt with a beast of massive proportions all while at the same time focused on the concept of helping the warrior blend in with their surroundings.
It may not be as important now, but back in the days of the tribal tattoos, it would be important to make sure that you are not crossing one tribe’s symbols with another as it may produce a very different meaning. Remember that the concept of tribal tattoos are that of a story of time and therefore each individual depiction is a form of hieroglyphics which when combined with another tattoo later may tell a story that may be less than what you are looking for.