I thought up some additional signs to supplement the witcher's sign set. Shadi, Volun, Runa, Vorg, Vintyr, and Moahk.
Shadi: Could produce a short period of intangibility, its alternate form would be short period of invisibility.
Volun: Would produce bolts of electricity from the witcher's hand, its alternate form would have a chain lightning effect.
Runa: Would produce a light from the witcher's hand which would magical translate runes or magical writing, its alternate form would allow witchers to inscribe runes in any surface with their fingers.
Vorg: Simlar to Quen but able to be walked away from by the witcher useful for producing a barrier to block one entrance so the witcher could defend a different entrance point, its alternate form would create a selective barrier that would forcefully sling back any hostile or unwanted forces that tried to cross it.
Vintyr: The exact opposite of Igni, Vintyr would produce a flash freeze wave of ice, its alternate form would shoot a sustained blast of ice and frost.
Moahk: Would produce water, and could be used for survival situations. Its alternate form would produce pressurized burst of water similar to modern day water hose blasts.