Elephants are fascinating but the beliefs you just read about are based on misunderstandings of elephant behavior.
First, we should not assume that old elephants are aware that they will die soon just because they break away from their herds. There is a very practical reason why old elephants leave their herds. You see, when elephants get old enough, their teeth become more down and they have difficulty chewing. So elderly elephants wander away from their herds to look for soft vegetation that’s easier to eat. Soft vegetation is usually found near water. That’s why many old elephants graze near water and eventually die there, an area we’ve come to call “elephant graveyards”.
Second, the issue of whether elephants have artistic ability. If you want elephants trained to paint, you’ll notice that human trainers stroking the elephants’ ears whenever the elephant moves the paintbrush. Elephant ears are very sensitive and touching them in certain ways can be used to train the elephants to do tricks. The trainer teaches the elephant to remember certain patterns of paintbrush strokes and then encourages the elephant to repeat the brushstrokes by touching its ears. So an elephant using a paintbrush is just painting lines it’s been trained to paint. It doesn’t necessarily know that the lines are supposed to represent flowers or animals.
Third, Pliny the Elder and others are misinterpreting the reaction of elephants to mice. Elephants that react fearfully to mice aren’t reacting to the mice themselves but to the fact that mice are unfamiliar to them. Being cautious about unfamiliar animals is a natural instinct. But elephants that live in environments where mice are common, like elephants in zoos don’t react with fear to the mice. Clearly, once elephants become familiar with mice and realize that they don’t pose a threat, they don’t mind them.