A couple of monsters that didn't feature in the Thunderbirds TV series do appear in several specially created photos taken by Century 21 stills photographer, Doug Luke, who sadly died at the beginning of the year.
Another monster which I can't say I've seen anywhere apart from the covers of TV21, again featured in that same Thunderbird story.
I imagine it was specially made by the Century 21 model makers for Doug to photograph in his own studio space which he used to create scenes not seen in the actual filming.
A posed shot of Thunderbird 1 being attacked by this monster. This same shot was used a few years later for a Thunderbirds Special published by Polystyle.
You can see Doug being interviewed on the Film in Supermarionation documentary, and here's a link to an article by James Fielding about Doug as featured in the Independent newspaper.