Post scans dude! I never did have the opportunity to have own either Metroplex and Trips! I remember quite some time back someone posted pictures of the combiner gimmicks with Metroplex; which looked awesome in my opinion!
The art is by Magami Ban (nice name for message boards), he also did the character designs for earlier Japanese TF TV series
I scanned in a collection of all the Art Gallery pics through 2010, including the one you mentioned with Grimlock. http://www.tfarchive.com/comics/japanese/gallery.php