Ramage, 29, and Garvan, 25, have signed two-year deals which tie them to the club until the summer of 2015.
And both will be part of the Palace squad which starts next season in the Premier League after an eight-year absence.
Garvan, who arrived from Ipswich three years ago, scored four goals during the club's promotion campaign.
And Ramage, who featured in 40 Championship games in his first full season since joining from QPR, finished with the same tally.
Jazz Richards and Alex Nimely, meanwhile, have returned to Swansea and Manchester City respectively following the end of their loan deals.