I think your file system has gotten corrupted.
What you do depends on how valuable the photo are to you.
-- High value, see professional help. drivesavers.com
-- professional help is too expensive and you want a quick fix. Try a safe boot.
Shutdown your machine. Hold down the shift key. Poweron. The boot up will take longer than normal because the filesystem on the startup drive is being checked and repaired as needed. All about safe mode including what features and apps safe boot leaves out. Safe boot uses a software driver instead of using your machines video hardware.
Use safe mode to isolate issues with your Mac - Apple Support
-- stop using the disk the files are on. get an external drive and install macOS on it.
try one of several data recovery apps.
you didn't say what version of macOS you are using nor what file system... Please check what versions of macOS these tools work with and what file system.
Perhaps Disk Warrior will be of some help:
http://www.alsoft.com/DiskWarrior/
"Stellar Phoenix Macintosh - Mac data recovery software, recovers
data from damaged, deleted, or corrupted volumes and even from
initialized disks."
They have a trial version, so I guess you can see if your data can
be recovered...
http://www.stellarinfo.com/mac-data-recovery.htm
"Data Rescue II is the best data recovery software on the market for
recovering files from a problem hard drive. Data Rescue II works
when other tools fail. Data Rescue II is also completely safe to use
since it does not attempt any risky repairs to the drive while its
scanning."
http://www.prosofteng.com/products/data_rescue.php
FileSalvage is an extremely powerful Macintosh application for
exploring and recovering deleted files from a drive or volume.
FileSalvage is designed to restore files that have:
-- been accidentally deleted.
-- become unreadable due to media faults.
-- been stored on a drive before it was re-initialized/formatted.
http://subrosasoft.com/OSXSoftware/index.php?main_page=product_info&products_id=1