As you enter the Castle from the front, you can look to the left and right and see the lights along the water. You can also see them if you're walking up the side path from Sleepy Hollow to Fantasyland.
They're positioned so that they're hidden from most views.
And as the other poster said, there are additional lights on the upper levels of the Castle to help light the upper sections.
There are actually two types of lighting fixtures used. The larger ones that are most-visible in the aerial photo are moving-light fixtures inside weatherproof enclosures. These are what project the patterns, images or other moving lights onto the Castle during Wishes, the Kiss Goodnight, etc. These can also be used to supplement the floodlights when the designers need them.
The floods are smaller units (I think they're now all LED fixtures) which can sort of be seen in the aerial photo between the larger fixtures and the water. (Easier to see on the Liberty Square side in the photo) These are strictly color-changing floodlights.