As you may know, Noriyoshi Ikeya designed the hero Silver Kamen and the aliens that appeared in the Silver Kamen episodes while I am not sure if he designed all of the aliens featured in the show (I think all the “Silver Kamen” and “Silver Kamen Giant” aliens were sculpted by Ryosaku Takayama).
At least the aliens I saw in the episodes screened at the event were surely designed by him, and they were: Alien Tigris (Episode 1); Alien Khimaira (7); Alien Solomon (8); Alien Domino (9); Alien Titan (10)
It is said he dared design Silver Kamen and the aliens not to make them look extremely strong, and, as the result, all these characters have their own unique forms and atmosphere distinctive from the equivalents of the Ultra Series.
It should be only natural as the show itself is said to have been plotted and produced with a strong sense of rivalry against the big-name hero show Ultraman.
It should be partly because the Nihon Gendai Kikaku (Japan Modern Planning) and Jissoji-led Kodai Group that were involved in the Silver Kamen production had many people who had to leave Tsuburaya Productions for the company’s financial reasons.
As to the Silver Kamen aliens, they were not unilaterally evil but were set to try to rob Kasuga brothers of the hidden photon rocket engine blueprint because they thought earthlings would invade their planets if the rocket should be completed.
Against their expectations, children watched “Mirrorman” aired in the competing timeslot a lot more as an orthodox tokusatsu hero show while the human-sized Silver Kamen didn’t play an active part at all in the show centering on the stories about the agony of Kasuga brothers.
I remember, however, I watched “Silver Kamen” and “Silver Kamen Giant” more than “Mirrorman” in my childhood somehow, and I have found the Silver Kamen aliens attractive enough again this time.