Complete a character's Combo Challenge to unlock his or her artwork at the "Gallery" menu.
Complete all five normal trials in Challenge mode with the indicated character to unlock the corresponding official picture at the "Gallery" menu.

Official 3: Ryu and Ken.
Official 4: C. Viper.
Official 5: Abel, El Fuerte, Rufus or C. Viper.
Official 6: Chun-Li.