THR reports Bokeem Woodbine has been cast as another bad guy, though the role is unknown.
Better Call Saul's Michael Mando may be playing some sort of villain as well.
While shades of Spider-Man 3 come to mind, bear in mind some of these villains could simply be "bad guys," meaning drug lords or burglars and not necessarily super villains.
It's also possible they could be setting up super villains down the road (Sinister Six?), with the actors playing their alter-ego in Spider-Man: Homecoming (i.e. Norman Osborn; then a later movie sees Green Golbin).
"Spider-Man: Homecoming" has a July 7, 2017 release directed by Jon Watts also starring Robert Downey Jr., Michael Keaton, Marisa Tomei, Laura Harrier, Tony Revolori, Michael Barbieri, Kenneth Choi, Martin Starr, Donald Glover, Isabella Amara, Jorge Lendeborg Jr. and JJ Totah.