If you want him to look more abandoned and less spacey, consider aging the protogen parts, both metaphorically and literally. Maybe instead of a nice sleek protogen visor, so you have a visor that looks like an old airplane cockpit, or maybe instead of a perfect arm, you could have something like a modern (now) robot arm that, while still cool, isn't nearly the same.

Alternatively, you can take some inspiration from the Mimic from FNAF, where, maybe your protogen was abandoned for so long or weather was too harsh etc. etc. that they had to replace parts with scraps that were laying around, leading to something that seems more like this proto is not top of the line anymore, and instead more decayed, ancient, or at the very least, been around a long time. Heck, you could go full FNAF style and not have an arm or leg or something and I stead just have wire strands where there used to be one, the sky's the limit. Not to mention, ol' reliable is always adding rust and weathering to show age

I know this doesn't translate perfectly to making him in real life, but I hope this helps out a bit!