The West Ham and Manchester United loanees follow Kevin Doyle, Dellatorre and Aaron Hughes in moving to Loftus Road on the final day of the January transfer window
Maiga has arrived on loan from West Ham until the end of the season, with Manchester United youngster Keane, who spent time on loan at Wigan earlier this season, agreeing a similar deal.
The Championship promotion-chasers had already brought in Kevin Doyle, Brazilian striker Dellatorre and Aaron Hughes on Friday.
Discussing the arrival of Hughes, Rangers manager Harry Redknapp told the club's official website: "Will is a young player with fantastic potential.
"He's got a good eye for goal, leads the line well and will provide us with good competition in the final third."
The Loftus Road side sit second in the table as they bid for an immediate return to the Premier League but have made the scramble for forward signings after top scorer Charlie Austin suffered a serious shoulder injury.