If you are storing digital / scanned images in SharePoint you are most likely storing them as Adobe PDFs.
PDF is a great format to use because it views nicely and it also can accommodate full text searching of text in the image (more on that another time).
If you are now looking to implement records management for those documents this infers a requirement to keep the images for a long time.
This is where PDF/A comes in. It is a reduced feature set of PDF which is guaranteed to be viewable in years to come whereas perhaps a more fully featured PDF document might not be in a couple of decades time.
If you are scanning your documents into SharePoint the scanning software should be able to generate PDF/A compliant images for you though there might be an additional cost for this.
If you are migrating scanned images into SharePoint then it is worthwhile ensuring that these are generated as PDF/A compliant.