For the visuals, I'm very much imagining a world somewhat like the one Gibson describes in Neuromancer - a mixture of bleak futuristic city scapes full of shadows and high-tech lowlifes (similar to Bladerunner), bustling city centers filled with holographic advertising (think Akira or Transmetropolitan), clearcut wastelands immediately outside the cities, and lush forests in the wilds far outside the cities.
For the characters, I imagine soldiers and rogues to be covered in futuristic robotic power armor full of little lights and energy lines, psychics radiating bright auras, and hackers covered in high tech devices.
Right now, I have 27 branching classes with over 250 skills total planned for the game. Here are some examples of classes:
Hacker: A high tech criminal capable of infiltrating enemy electronics and implants, the hacker has skills that allow him to take over enemy gun emplacements, hack enemy's implants to cause them to have the opposite of their intended effects, and even hack enemy nervous systems to take free attack actions with them.
Phantom: A rogue/psychic hybrid who uses his psychic powers to push his body to the limit, thus using his own life force to cause overwhelming damage to enemies.
Neuromancer: A powerful psychic capable of reading and influencing enemy thoughts, able to cause overwhelming fear and even suicidal tendencies in enemies.
Guru: An incredibly knowledgeable chemist, the Guru has become obsessed with bringing the effects of psychogenic drugs to the masses and has effectively weaponized hallucinogens and other drugs to cause all kinds of horrible (and hilarious) effects to enemies on the battlefield.
I looked around the web and here are a few inspiring pieces of art I've found that resemble the visuals I want in this game:
An awesome cyberpunk cityscape.
Another.
A "wired" warrior.
A "wired" rogue.