Concept art (in both modes) was included for Iguanus and Bomb-Burst. In addition, art was included for several characters not featured in the series such as Cosmos (robot mode), one of the Seekers (with 2 different robot and alternate modes) and Astrotrain (3 modes).
Concept art was included for both Iguanus and Bomb-Burst, as well as several other characters that were not part of the main series.  Cosmos, a robot mode, one of the Seekers with two distinct robot and alternate forms, and Astrotrain in three modes are all examples of this.