Import the images into another table, then use a script to find the appropriate record and link the two in a relationship.
The Import Records | Folder tool can import the image files into a container and the filename into a text field at the same time.
Then it's a matter of the script finding and linking records.
Assuming a 1 to 1 relationship, you can define a serial number field in either table (you may have one already defined in your current table) and set up a match field for the relationship in your new imported image table. With either method, your script would link your image record to a record in your existing table by copying the serial number to the match field.
How you set up the script will depend to some degree on the design of your current table and whether your imported images will replace existing images or not. If there is a consistent format to how the additional characters are added to the record name to make it a filename, this can be set up without needing to use a script as a calculation field can then extract the record name from the file name and then it can match to the recordname in the relationship.
Thank you so much!!! Have a great weekend!! :)