When selecting photos, you should be selecting from Royalty Free (RF) images and videos.
Hero pictures are responsive in nature. Responsive pictures are automatically re-positioned and re-sized in response to the size of the viewing area on the device (PC, Tablet and Phone). Because hero pictures are responsiveness to screen size, these pictures require a large bleed (the border extending beyond the subject).
Below are several examples illustrating the main subject of the picture contained in the yellow "subject guide" and the area outside the yellow box is the bleed.
Failure to create a large enough bleed results in the subject area being cutoff on certain viewing devices.