These photos need to be labelled as either the Student ID or UPN and be a jpeg or PNG file.
Example:
1234.png
H99899891801D.jpeg
If the file have any other numbers or letters, or they are not the correct file format, you will not be able to use the bulk importer.
Scholarpack automatically scales them to be at a resolution of 180x180 and a file size of 13Mb. Sometimes the scaling can pixelate the photos if the resolution is too high or the photo is too rectangular, so ask the photographer to try reducing the resolution or cropping them into a square shape if this happens.