Ideas are a dime-a-dozen. In truth, you can have some of the best ideas but its all in the execution of them. That being said, I figured I'd let you in on my process, so you can see where the ideas start and break down from there. It's a long and involved process, but this is where it starts.
Fair Warning: In discussing these ideas, there is a great chance that I will spoil for you where the story is heading, or, in the case of sequels, where the last book ended. If you would rather not have these story lines ruined for you, don't read further.
My point still stands though: ideas are cheap - it's the execution that matters.
A re-imagining of my first novel, Between the Shadows. The original novel's premise still stands but with a much more focused setting. Borrowing from Auroville and the Kowloon Walled City, Convert35 will be a much darker, dirtier version of its previous city. Cameras are set up throughout each passage, allowing those who are skilled to move out of their reach.
The Traveling Survivor
As odd as this will sound, this was inspired by a failed game of Civilization V. The basic concept is what if a man from a destroyed civilization escapes out into the full world and, while moving between cities trying to survive, he sees the remnants of his culture in every city. On his journey, he finds out that he used to be a part of the most powerful race, but they were slowly whittled down and destroyed.
Sequels to The Faithful
Now these are going to consist of multiple books, some of which I'm developing as this is being read. To start out with (SPOILERS) Sandhyanen is in shambles, no one has seen Raine and most reports are that he died, though no one was able to reproduce any body. The last time we see Raine, he's traveled with Marise and Senwe to parts unknown. Urban is left to fit the pieces back together of Na Creidmhigh and his confrontation with Carrick has left him in shambles, possibly worse than his predecessor.
The way I see it, these novels then spin off in two different directions: one follow the gods and their trials, the other sticking with the humans and how they react to the gods' intervention and casual destruction. Now, admittedly, the human story line could be a B-Plot in the next novel, but I'm trying to give it the same heft that I did with the first novel.