image_top
aligns the image to prioritize the top edge (ie. this can be useful to ensure people's heads are not cut off in photos)
image_bottom
aligns the image to prioritize the bottom edge (ie. this can be useful if there is excess space at the top of a photo)
image_left
aligns the image to prioritize the left edge
image_right
aligns the image to prioritize the right edge
image_center
aligns the image horizontally centered
image_middle
aligns the image vertically centered
You can also use these in combination. For example:
image_top, image_left
aligns the image to prioritize the top and left edges