SM Stirling's Emberverse books are set in a world where electronics, internal combustion engines, gunpowder, and a wide range of other technology just stops working. Initially that's the only speculative element, but as the books progress, it becomes more and more a matter of high fantasy.
It has an effect- the more intriguing the cover, the more likely I am to pick it up and look at it. But I've bought books with ugly covers and passed up books with nicer covers if something else about the book strikes my fancy or makes me lose interest.
I'd suggest looking at general religious themes. For example, the death and rebirth motif is quite common- from Christ to Adonis, Baldr to the Hero Twins, Orpheus to Blue Jay. Whether it's literal physical death or a descent into the Underworld, it comes up a lot. Other common themes include...
Unusual ways to protect yourself, hmm? *cracks knuckles*
Well, apart from talismans and religious medals, there's a wide variety of formulaic gestures and sayings, from crossing yourself, to the sign of the horns, or recitation of various religious formulas or prayers (I.E. "May the saints...
I'm not quite sure your argument is what you think it is. You mention the Old Masters, and say that fiction being an equivalent to there work is part of why you feel that painstaking research adds nothing or even detracts from fantastic fiction.
I would point out that many of the Old Masters...
I used to write magic as a 'one more tool,' type thing, but lately I'm leaning more towards the sort of inherently magical world- somewhere between Grimm's fairy tales and Lovecraft if that makes any sense.
I think conflict after the climax can serve to make an important point- that there aren't necessarily one hundred percent easy answers to complex problems. Just because you killed the evil overlord doesn't mean that the fact that he's been burning crops for the past six months of his campaign...