If it's for a UK passport make sure it's on a light grey background. I had mine done here in a Kodak store, explained what they were for and they were rejected at the passport office because the background was too light.
Any Kodak or other photo shop in any mall will do them, be sure to mention which country passport photo it is as the requirements differ.
UmmSuqueim has one in the Spinneys there, in Jumeriah the Mercato mall has one, Oud Metha Lamcy Plaza,, and Mirdiff City Centre and Festival City mall.