Peacemaker was proof that the DC Extended Universe is capable of presenting its characters in a fun, serialized way. Marvel already has the jump on making superhero series a critical component of the streaming television experience. DC's darker themes could either lend themselves to streaming series. Alternatively, there is plenty of light-heartedness and comedy that could be called upon. DC already has quite a history of TV adaptations, both animated and live-action.
The DCEU has already introduced many characters who could lead their own series. From beloved Harley Quinn, to the more obscure like King Shark, there is a wide variety from which the franchise can choose. If the DCEU's ultimate goal is to team up more of its characters, it would perhaps be better if fans got to know some of them on a deeper level. TV series are the perfect venue to dig into characters' backstories and motivations, before teaming them up in future franchise entries.
Harley Quinn
Margot Robbie's Harley Quinn has appeared in several DCEU projects so far. A very different version was introduced in Suicide Squad, followed by Birds of Prey and The Suicide Squad, in which the character was much more designed for the female gaze.
A Harley Quinn series could take several possible directions. It could be a continuation of the Birds of Prey story, and see her team up with other female anti-heroes and villains. Alternatively, a series centered Robbie's Harley Quinn could also be similar to the animated series.
King Shark
King Shark may be a being of few words, but he has certainly made his mark on this franchise. His first DCEU appearance was in The Suicide Squad, a member of Task Force X. His brutality was offset by his monotone, one-to-two-word humor.
A King Shark series could work well as a comedy. Each episode could be a self-contained adventure, where King Shark introduces some of the most outlandish DC characters as they make their on-screen debuts. The comedy could offset the darker tones of the DCEU.
Leota Adebayo
Adebayo was an integral part of the Peacemaker series, as the daughter of Amanda Waller. She was a complicated character, trying to do the right thing, with questionable methods. Danielle Brooks brings the perfect amount of heart and humor to this role.
An Adeayo series could be an extension of Peacemaker, in the sense that viewers could follow her journey being given various assignments by her mother. This would also be a venue for the character to be incorporated into future Suicide Squad projects. This could be a dark cop comedy, that Brooks would be more than capable of leading.
Lois Lane
There would be no Superman without Lois Lane. Amy Adams' version was first introduced in Man of Steel, and subsequently appeared in both Batman v Superman: Dawn of Justice, and Justice League. Adams' version of the character is a very hands-on journalist for the Daily Planet.
A Lois Lane series could be a journalism procedural, similar to The Wire. This would be an opportunity for the character to be flushed out more. Lois Lane has a lot of journalistic prowess that is perfect for a DCEU series.
Cyborg
Ray Fisher's Cyborg was introduced in Justice League. He was re-constructed after a car accident that killed his mother and nearly killed him as well. His screen-time so far has been limited, however, this is a character with a lot of potential.
A Cyborg series could be an origin story. With this character's history of being a high school football star, this could be a high school drama, following Victor Stone in the years before he became Cyborg. Fans could get to know this character more, and look forward to his appearances in future DCEU entries.
Rick Flag
Rick Flag has had a mixed history within the DCEU. He made no friends with his introduction in Suicide Squad, which saw his character spew exposition. His character received a better reception in The Suicide Squad, as he was given more of a complete story.
While he may seem like an odd choice to headline his own series, there is more that can be done with this character. He's a misfit leader who's supremely unqualified to do most of the tasks he's assigned. A slapstick comedy featuring Flag's misguided leadership could make an enjoyable DCEU entry.
Antiope
Robin Wright's Antiope was a feature of Wonder Woman before her tragic demise. She returned in Wonder Woman 1984, in a flashback recalling Wonder Woman's training as a child. This Amazonian General was featured very briefly, but made her impact on known.
An Antiope series could be a war epic, chronicling her backstory leading the Amazons. This would give fans a chance to get to know Antiope more, as well as further explore the Amazon military. This would be a female-led project that would make a fine addition to the DCEU.
Mera
Amber Heard's Mera was introduced theatrically in Justice League in a very brief appearance. She was Aquaman's main love interest in that character's solo movie. The comic canon focused more on this character's own powers and storylines, having Mera join the Justice League.
Although this character received generally mixed reviews from fans and critics, a series could give this character a new lease on life. Taking a cue from the comics, Mera could have her own story and character development. This hypothetical series could also be a venue to further explore Atlanna as a setting.
Mary Bromfield (Mary Marvel)
Shazam! was a superhero story about family. One member of that family was Mary Bromfield, or in the comics, Mary Marvel. In many ways, her character is the heart of Billy Batson's found family. With her siblings, she gains superhero abilities.
Really any of the Shazam! siblings could carry their own series, further exploring Shazam lore. However, Mary as the leader is the natural choice to explore how this family navigates their new abilities. This series could certainly be a comedy, or it could follow Mary fighting supervillains while starting college and trying to live a normal life.
Huntress
DC has a lot of room for vigilantes, and Huntress is a top-tier one. She was introduced in the DCEU in Birds of Prey alongside Harley Quinn and Black Canary among others. She has not yet been seen since, but her introduction was compelling.
Huntress's story could be an Equalizer-style vigilante story, with the character being hired to solve a new crime each week by those looking outside the law. A series could set up future Birds of Prey stories, or at least a Harley Quinn team-up. This series could also go in a completely different direction by being something of a workplace comedy, showing Huntress working with a motley crew.