Looking in WI issue 322, I just found that Gripping Beast were asked if any new figures were to be released, the answer was yes. They make mention that while they are using some of their favourite figures from their existing ranges, they supplemented all the factions with many new figures. The starter warbands and re-inforcement blisters will be released in three waves: Crusaders and Saracens; Milites and Mutatawi'a; and then Moors and Spanish.
Looking at page 84 of C&C, those camel riders look GB in style to me. I suspect they are yet to be released models.
Maybe email GB and ask if and when they will be releasing camel riders.