There are several ideas from the DC comics that could be used for a DC movie or TV show. Some of these ideas have already been hinted at in the movies and TV shows.
For example in Batman vs Superman we see an old Robin suit with the words ha ha written on it. This is a reference to Jason Todd who was one of the Robins that was seemingly killed in the comics and returned as the red hood.
Batman vs Superman also seemingly has a reference to injustice where Superman turns evil when Lois Lane dies. This can be seen when the Flash appears to Bruce Wayne and says it is all about her.
Another idea that was used a little in the flash TV show was the flash point event. I would like to see this in the movies so that we could see how it would affect the other characters like Batman, Wonder Woman, Cyborg, and Superman.
It could also be interesting if they use a multiverse idea in the movies, just like in the TV shows. They could even use this to have a movie and TV crossover if they wanted.