OP:
You should realize that professional data recovery firms can be VERY expensive. Expect to pay upwards of $1,000 or more to get the data back.
Also -- I realize it hurts to find this out now, but this is why one NEVER stores PRECIOUS data in "only one place". If the photos on that drive were important to you, you should have had at least one backup, maybe two. Go forth from this day, and learn, a sadder but wiser man.
Having said that, I was in a similar situation once, having lost a few thousand mp3 files on a partition that went bad on me. Nothing I tried could get that "lost partition" to mount up again. But I was finally able to get most of the data back, without having to resort to professional-level data recovery.
Here is how I did it.
First, I had an empty external drive to serve as my "scratch drive" (drive which would receive recovered files). You will have to buy one, too. I suggest you get a "bare" drive and a USB3/SATA docking station.
I used "DataRescue" as my recovery app.
(I see you already have Stellar Phoenix, you could try that first, or do a free download of DataRescue3 and see if that helps).
Because the partition was corrupted, it would not "mount on the desktop", and DR couldn't "see" it. How could I get DR to recognize its presence?
I RE-INITIALIZED the entire drive (yes, you're reading that correctly).
HOWEVER -- and this is VERY important -- I DID NOT select to "zero out" the drive.
If you zero-out the data, it will be UNRECOVERABLE. DO NOT DO THIS!
I just re-initialized it, creating a new directory, but leaving the old data "intact" out there on the platters of the drive.
Now the drive would once again mount on the desktop.
Of course, to the finder, the drive now shows as "empty" (because it has a new directory).
BUT -- data recovery apps are able to "bypass" the directory, and "go right to the platters" to find lost data.
Thus, DR was able to "look around" the "empty" directory, and it spent some time scavenging the drive. It FOUND the old data, and re-assembled it and saved it to the scratch drive. Just about everything.
IMPORTANT TO REALIZE:
Data Recovery software, because of the way it works, can find old data, but in the process of doing so it may not be able to recover file NAMES -- just the data itself. Nor will it recover previous folder hierarchies. You may be left with a pile of un-named files that you have to sort out yourself. This is "par for the course" with data recovery, and you should consider yourself happy just to get the files themselves back.
A TRICK THAT MAY WORK:
Because you are trying to recover old pics, which have "metadata" as well as regular data, you might be able to dump the entire batch of recovered pics into iPhoto (or another photo organizing app). iPhoto will then "read the metadata" (which I believe also contains file names) and you may get some of your previous "organization" back.
I discovered that by creating an entirely new iTunes library, I could re-organize the "lost files" back to an approximation of where they were. In some cases, I still had to manually rename files using the finder. YES, it's a lot of work. But consider the alternative.
Finally -
NO PROMISES regarding the above procedure -- but it worked for me on a corrupted drive when it seemed that all was lost.
I sense the procedure above parallels what many of the "professional" data recovery outfits try first. That is, a) reinitialize and b) scavenge.
This is "forensics" on a "software level", before "going to hardware"...