The Giant Robots are on parade here in #StarKnight, and one doesn't need to look long or hard to see both the Real and the Super versions out there. That means that you're going to find influences from the big boys on both sides--Gundam, Macross, Mazinger, Getter Robo--because it's impossible to avoid them; I won't get into them here. Instead, this is going to talk about lesser-known shows/manga/etc. that went into what's going down.
For the Real Robot side of things, the Knights In Giant Robots thing is what you should be noticing. That means Dunbine, Galiant, and Escaflowne (albeit with beam swords) because these heroes and villains get into sword fights in and out of their mecha. Just swap to lightsabers and you can see how and why I did just that with #StarKnight. Juxtaposing them are the GERWALK-style mook units such as the Goblin and Hobgoblin that Red Eyes makes his men pilot into battle (and, like their namesakes, die in droves), taking their cues from Orguss and Srungle.
For the Super Robot side, where some say "They're superhero stand-ins." I went one step further and (following Mazinger) made them mythology references. There's two in Book One, both are not subtle about what they refer to, and they do all sorts of Laws-of-Physics-Are-More-Like-Suggestions sort of shenanigans. Sure, you'll get your blazing swords and rocket punches and called out attacks, but there's a little bonus for those who know their mythology/history. They're at the level of plot-devices in Book One, but you'll see more of them as we go along.
Being that Book One is our introduction, the crazier stuff mecha shows have done are left out; gotta save something for the sequels. I'm doing some avoidance of well-known tropes in many of these shows, Super and Real alike, while changing others to suit my purposes. (If you're looking for Typical Mecha Protagonist, you want to keep an eye on the page--Creton--as he grows over the series; Roland's more like The Shadow or James Bond in that he's an Iconic Hero.)
Speaking of Later Books, here's something you can look forward to seeing, in terms of inspirational images: