Using the Mp3tag application (http://www.mp3tag.de) you can apply the Mp3tag action ... "Import cover from file". This imports the cover art specified by the absolute or relative filename into the tag of the file. You can use placeholders like %artist% or %album%. You can use wildcards like ? or *.
So it should be feasable to do ... having ...
music file: Queen - Bicycle (128kbit).m4a
image file: Queen - Bicycle (HQ).jpg
... apply action ...
"Import cover from file".
Format string for image filename: $regexp(%_filename%,'\(.*$','*')
Import cover as: Front Cover
For image filename which is not exactly the same as the music filename, you may use a format string like ...
$regexp(%_filename%,'\W','?')'.jpg'
==> "Queen???Bicycle??128kbit?.jpg"
... this replaces all characters, which are not letters or numbers or underline character, with the ? wildcard.
$regexp(%_filename%,'\W+','*')'.jpg'
==> "Queen*Bicycle*128kbit*.jpg"
... this replaces all sequences of characters, which are not letters or numbers or underline character, with the * wildcard.
$regexp($regexp(%_filename%,'\(.*\)$','*'),'\W+','*')'.jpg'
==> "Queen*Bicycle*.jpg"
... this replaces all sequences of characters, which are not letters or numbers or underline character, with the * wildcard, and removes the trailing parenthetical expression.
DD.20140503.1620.CEST