Yes, Jagger visiting you in a dream would be considered a "Dream Sign." I have read of constant examples. Not only with our beloved pet's of course, but among humans who have lost a loved one.
I read of a woman recently who lost her 3 young daughters as well as her Mother and Father a few years ago, in a restored Victorian house fire. The woman's boyfriend at the time, had carried a bucket of ashes from the fireplace one night and set the bucket outside on the rear porch, but the bucket was plastic and melted through, and embers fell through and caught the side of the house on fire. The upper floors caught on fire and the smoke tragically killed the 3 children and 2 parents.
As the woman grieved, she became suicidal. She was in her bathroom getting ready for bed one night and began to cry. She looked up and in the reflection of the mirror, standing right behind her she saw her 3 daughters, who had passed away. And they were all smiling at her and looked beautiful. The eldest said "Don't cry Mommy. The World of Dreams is more real than the World that you are living in." And then they vanished.
That moment saved the woman's life.