The lore introduced in Tai's Route is largely a mishmash of ideas I've had in the back of my mind for a long time. It's hard to say how I really came up with it beyond it being the culmination of a blend of media I've consumed over the years and my own misanthropic and nihilistic worldview. In a way, I had hoped to show that despite new life having taken up humanity's mantle, the inherent humanity in our successors is what leads them down the same doomed path our species in real life is currently seeing through to the bitter end. Despite some improvements, many of the same old human-made problems simply repeat themselves, as is our nature, and even though this new earth is no longer inhabited by humans, every single intelligent life form is half-human, and that is already more than enough. Ultimately, what lies ahead for them is unknown and open to interpretation. In that regard, my own predictions are no more valid than anyone else's.
As for the filtered photo backgrounds, some of these are original and others are stock photos. Anything we've used we've done so with the appropriate rights, creative commons or somesuch. When we started out, CurryCatz wasn't confident in his ability to render backgrounds and to expedite development, we simply utilized original photos or stock images to fill in the gaps. As it would happen, CurryCatz was actually quite good with backgrounds! These days, we rarely if ever use stock photos, preferring instead to draw original artwork, only using them where absolutely necessary to reduce his workload. Thinking back, the last time we used a stock photo I think was the alleyway on Tai Day 17, which was more than a year ago now! By the time we release 1.0, we're aiming to have original artwork for every background and no stock images anywhere.