Quick work if you have a webhook engine, which would write the results back to one or more fields. You would only need a single textarea field to hold all the images for a lead, since you could use a Velocity token to further parse the 4 URL values. Or you could write the 4 image URLs to 4 fields and just include them that way. (Of course, you could also merge the CSV into the database, since the import will dedupe on email address and that's the same dedupe key as in your CSV.)
Alternately, you could paste the entire CSV (it doesn't sound that big, if only 1000 lines of short text fields) into a Velocity token. Then use another Velocity token to search and parse it.