Are Leon's photographs real? I mean, if Rachael's photo was a fake, then...

Leon's photographs are almost certainly real; what would be the point of supplying replicants with fakes, considering they have no implanted memories to begin with and know they are replicants? Besides, the photograph Deckard examines with the Esper machine was evidently real enough to be useful (it showed the apartment, with Zhora and Batty).

I could swear I saw Rachael and her mother move on that picture.

Yes, they do move. Actually, what is shown is not a photo but rather a freeze-frame of a filmed sequence, which then, (for a very short moment), starts playing.

What is the scribbling we see on the back of Rachael's photo?

On the back of the photo there is what seems to be an address. This is certainly meant to be glimpsed, (it is shown on two separate occasions), but was probably never meant to be decoded precisely.

Of course we've tried anyway

Best guesses so far:

cas 4217
68W Thika Blvd
South Wenton
Waytton

[The last line is illegible; it might be some signature.]