have to be jailbroken and download ifile.
in ifile go to media/dcim and find the photo you want and copy it. next go to system/library/proceduralwallpaper/click next folder/edit/ and paste photo.
i have the shark wall under blue. So find the file that is shown in the pic. with blue_1k_v2.png. tap on i icon and add .bk behind png after you copy the file name. next find your photo you pasted in which will be a .jpg file (tap on icon) select name and delete then past in the blue_1k file name and you done. and just repring.
http://img.tapatalk.com/d/14/01/26/a2u8eva9.jpg
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