PSA has only started scanning cards recently, I believe they’ve scanned all cards submitted at re-opened tiers since they started. So unless the card was submitted recently, it would not have a scan on PSA’s website.
Example of one of my recent cards with scan: www.psacard.com/cert/63735134/psa
Example without a scan: www.psacard.com/cert/27690517/psa
Regardless, you do not need an account to view scans. They just pop up when you enter the cert number into PSA’s website. If you do that and scans don’t pop up, then PSA doesn’t have them. You could always ask the seller for some additional photos if you’re nervous.
In the future, if you have basic grading-related questions, you should post them here! www.elitefourum.com/t/the-giant-professional-grading-thread/30930/1