You don't say if it is a lost phone, stolen phone, deleted images, reset phone, etc.
If it is just that the images were deleted, or the phone was reset you 'may' be able to get them back. And I emphasize 'may'. If the phone was lost or stolen, then there is nothing anyone can do.
There are a few apps/programs out there that 'may' be able to help you recover the data.
A few of the programs you could try would be... DiskDigger, MobiSaver, Android-Recovery and Tenorshare. They are all data recovery apps/programs. There are many others out there, so check around and see which you would rather try. There is also one called RECUVA, that I have heard is free, which you could try.
One important note though, most of these programs are not...