Hero carousel, news story, faculty spotlight, and patient story feature images should leave the bottom 1/3 clear for heading overlap.
There aren't any other restrictions on composition in other areas. Ideal sizes (all 2x pixel density):
Nav megamenu: 1:1, 564x564
Home hero: 21:9, 2880x1136
Interior hero: 3:2, 1524x1017
Hero carousel: 16:9, 2640x1485
Patient Story: 16:9, 2192x1232
Faculty CTA: 1:1, 852x852 large, 406x406 small
Faculty Spotlight and Large CTA: 16:9, 1746x982
News Feature: 3:2, 1746x1166
CTA row: 1:1, 496x496
Card: 3:2, 630x420