How do you deal with first and last image then?

I insist on my belief that a primary key should be doing only one task, i.e. identifying the record uniquely. If you need a display id, you have two choices:

• Adding a field to your table for display purposes, but then you would have two further problems.
• filling the gaps when you delete a record.
• Always displaying the records in the same order. No chance of diplaying with different criteria.
• Creating a display number when you select the records. And you can do it either in (at least) two ways:
• with a MySQL variable.
  

  SELECT @count := @count+1 as sequence, id, name, filename from mytable
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• In your Perl script.
  

  my $query = "SELECT id, name, filename from mytable";
  my $sth=$dbh->prepare($query);
  $sth->execute();
  my @results;
  my $count =0;
  while (my $row = $sth->fetchrow_arrayref) {
      push @results, [ $count++ , @$row ]
  }
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  Now your @results have a counter that you can use for displaying purposes.
  Modifying your query with a different WHERE or ORDER BY will change the display order.