Though he isn't quite so well-known in the West, one of the greatest Transformers illustrators of all-time is Hidetsugu Yoshioka. In the mid 90s, Takara commissioned him to illustrate a series of "story pages" for the magazine Comic Bom Bom to promote their Super Turtles and Metal Turtles toylines. You can find a complete gallery of the pages at TFPulp, though they aren't of the best quality (they're large, but badly pock-marked).
However, Adam Winters got ahold of one of the issues that featured Yoshioka's art and sent me a high res scan, which you can enjoy below: