I thought it would be a cool post to show some of the things that were shown Pre-Flashpoint that have been incorporated in the Post-Flashpoint world whether it being big or small. Reason being alot of people don't think there's alot to pull from which apparently has been proven wrong by writers. If you have any feel free to share, I'll post stuff as I find them.
Dr. Shinobi to Dr. Shin
Pre-Flashpoint we had a Doctor named Dr. Shinobi who seemed to have a obsession with Dolphins. In this new continuity Dr. Shin that appeared in one issue has been expanded upon and put into Aquaman's origin to where he had an obsession with Arthur and finding Atlantis.
Pre-Flashpoint we had a group of powerful Dimension traveling Demons who were called The Others and seemed like more antagonist then protagonist, as of Post we have a group who traveled the world with Aquaman and deal heavily with his origin are they as powerful time will tell possibly but they weilding powerful Artifacts that were crafted by the next change on the list.
Atlan The Wizard to Atlan The Dead King. (Almost put Dad King :P)
Pre-Flashpoint for a while Atlan was said to be the father of Aquaman and Ocean Master which seemed to be later retconned in the Blackest Night/Brightest Day storyline. Pre-Flashpoint Atlan was a powerful mage who was suggested to be almost on par with Arion which says something. Atlan made enemies of The Otherworldly Demons known as The Others when he opened there portal and helped his family and Dolphin escape. As of the New Continuity Atlan seems to have gotten really pale and went from Mage to Warrior class. Atlan is responsible for the destruction of the continent of Atlantis and creator of The Artifacts the group know as "The Others" use.
Hy-Brasil and The Trench
The similarities between the two groups make it almost hard to distinguish though the Hy-Brasil seem to have more intelligence and are the weaponry of Ancient Atlantis their traditions make then highly similar to the trench as well as their habitat. The leader of the Hy-Brasil had a symbolic knife to show their kingship, The king of the Trench would use a scepter to control them. The Queen in both cases seem to be the head figure for both races and they live in the shallow part of the ocean in a somewhat trench. The Trench played a big role as the first antagonist Arthur and Mera faced in the Post-Flashpoint issues.
Other characters that appear in both continuities. Arthur, Mera, Orm, Vulko, Tula, Garth, Fire Trolls, Creature King, Tom Curry, Atlanna, Scylla, Charybdis, King Shark.
The thing that has me excited is there is still so much elements, characters, stories that could be incorporated into the Post-Flashpoint Universe.
I'll add to this as it goes on.