How Justice League Should Use Its DCEU Character Cameos
Justice League will tell the story of how Batman, Wonder Woman, The Flash, Aquaman, Cyborg and (a [...]
Lex Luthor
The recently confirmed return of Lex Luthor in Justice League is a big opportunity to clean up the mess fans got in Batman v Superman.
The DCEU would be better off if Jesse Eisenberg's Lex is found to be in full-on proper villain mode, with eccentric comedy left far behind. Rumor is Lex is the man who puts Deathstroke on payroll to hunt down Batman (and/or The League); that sounds like a good use of Lex to us!

Deathstroke
Joe Manganiello's Slade Wilson/Deathstroke doesn't have to do much in Justice League: just introduce himself as a formidable badass.
It'd be cool if he functioned sort of like his namesake, "The Terminator," by relentlessly hunting his prey (Batman), and causing major problems whenever he catches up to him. Having Deathstroke suddenly burst onto the scene to liven up any dragging moments would be a great introduction to the character - and a great safety net for Justice League.

Queen Hippolyta
Wonder Woman's mother has ancient knowledge of the DCEU that will not only come into play during Justice League (the mother boxes), but could open doors that extended through solo films all the way to a magic-based project like Dark Universe.
It may just be an exposition dump, but having Connie Nielsen's Queen Hippolyta drop Easter eggs is the kind of classy move we can get behind.
...Certainly better than video footage on Wonder Woman's laptop.

Mera
Amber Heard's Mera has already delighted DC Comics fans with a majestic seaside costume reveal image. In Justice League, we expect that Aquaman's queen will only give us a tease of her full potential - and that's all we want, really.
Meeting Mera as a regal badass who has little care for the surface world would be a good place to start, so that she later can evovle into a true superhero of two worlds, like her husband.
...If somebody threatens her king though...

Nuidis Vulko
Willem Dafoe's Nudis Vulko is Aquaman's oldest advisor. As DC comics fans know, the character's most famous arc was in the "Throne of Atlantis" storyline a few years back - which is an arc DC fans have hoped to see in live-action.
In Justice League, it's key to start setting up Vulko's skeptical and wary assessment of what's happening with surface world; that character arc could become crucial for the plotline of James Wan's Aquaman movie.

Iris West
Dope star Kiersey Clemons will play the movie version of Flash's love interest Iris West, and in Justice League, her mission is simple: Distinguish the movie version of Iris from the version on the popular Flash TV series, played by Candice Patton.

Lois Lane
If Lois gets something to do other than being in constant peril and/or worry, that would be progress.
Seeing her brass-balled reporting skills actually working toward the progressing the plotline would be icing on the cake.
A non-awkward kiss with Superman is almost more than we're willing to hope for...

Commissioner Gordon
The new Commissioner Gordon needs to make his presence known in the DCEU quickly, effectively, and will hopefully overlap the fond memory of Gary Oldman's Gordon from The Dark Knight trilogy.
If anyone can pull that feat off it's J.K. Simmons - who could help convey Batman's tragic history with just a weary look in his eye. Here's hoping Simmons' Gordon doesn't have any hints of J. Jonah Jameson; that would pull fans right out of the movie.

Alfred
Jeremy Irons' Alfred just needs to be there and keep doing his thing. Another spectacular pair of glasses would be a gift to fashionistas in the audience.

Darkseid?
Fans want to see Steppenwolf's boss - but they have also always maintained that Darkseid is a DC villain who needs ample space to be properly introduced.
For Justice League, we just want to taste of Darkseid's power (Omega Beam kill FTW!), or the big reveal that he's actually main focus of the story. There can be no in between.
For our part, the violent introduction of a terrifying archvillain is how we'd want it done. How about you?
