Can a solar eclipse be directly overhead? I have trouble picturing eclipses and whether the moon can be directly overhead.
They could be directly overhead if you live in the tropics. 

The tropics are the regions near the equator, between 23 degrees North and 23 degrees south. In the tropics, the sun and the moon can pass directly overhead. If both pass overhead at the same time there will be a solar eclipse directly overhead.

The eclipse of July 11, 1991 was visible directly overhead, (to within a degree) and in totality, for observers in the Nayarit province in Mexico