Like these?
Eucharistic Miracle of Lanciano
The Tilma of Guadalupe
Incorrupt bodies of the saints
Fatima
Shroud of Turin
Sudarium of Oviedo
In 1977 Ruth Carter, Jimmy Carter's sister, helped Larry Flynt convert to Christianity. At the moment of conversion, Flynt said that he saw (paraphrasing) "the heavens open, cherubs, the usual thing." Usual? Not for any Christian that I know.
He continued (again paraphrasing), "But my psychologist helped me to see that this was just a figment of my imagination. Just wishful thinking."
In other words, it's possible to even deny one's own sensory experience, especially if one wants to. The power of rationalization can't be overestimated.
Most importantly, we are not in a position to tell God what He should reveal to us, since His Wisdom is so far above ours.
27 Then he said, I pray thee therefore, father, that thou wouldest send him to my father's house:
28 For I have five brethren; that he may testify unto them, lest they also come into this place of torment.
29 Abraham saith unto him, They have Moses and the prophets; let them hear them.
30 And he said, Nay, father Abraham: but if one went unto them from the dead, they will repent.
31 And he said unto him, If they hear not Moses and the prophets, neither will they be persuaded, though one rose from the dead.
Thank you for your reply. Every time I ask this kind of question to a priest, I get similar answer, we don't understand every thing that God does.
However, it seems to me that it could be more efficient to have undisputed long lasting appearance that is capable of speaking to us in our languages all over the earth? For get that shadowy thing, and the nonspeaking crying virgin thing.