How Many Pictures Does A 16gb Flash Drive Hold?

It depends on the several factors like size, file types, resolution of the picture.
But on an average the file size of general photograph varies within 1MB-5MB. Your picture can be larger or smaller than average.
So normally you can get 3276 - 16384 pictures with a 16GB Flash Drive.

Guessing each image is 3-4MB and 16GB is 16,384MB.

Around 4681 images.

About 30.000