The kink.com properties use the following URL format for their free pictures:

    http://promo.wiredpussy.com/g/1/4591/i/1/h/
                                    ^^^^

That's the only number that matters.  IDs are unique across ALL kink.com websites, and you can even
display images from a different website, eg. the above page that belongs there can also be viewed
elsewhere:

    http://promo.fuckingmachines.com/g/1/4591/i/1/h/
    http://promo.hogtied.com/g/1/4591/i/1/h/
    http://promo.sexandsubmission.com/g/1/4591/i/1/h/
    http://promo.ultimatesurrender.com/g/1/4591/i/1/h/
    http://promo.thetrainingofo.com/g/1/4591/i/1/h/
    http://promo.waterbondage.com/g/1/4591/i/1/h/
    http://promo.whippedass.com/g/1/4591/i/1/h/


        However, this is only true for image_IDs >= 1000.  When they're <1000, those images are
        specific to that site.  For instance, these are different:

            http://promo.fuckingmachines.com/g/1/1/i/1/h/
            http://promo.hogtied.com/g/1/1/i/1/h/
            http://promo.wiredpussy.com/g/1/1/i/1/h/

        There doesn't seem to be a real order to the IDs though:

             998 sexandsubmission  (3043)
             999 --none--
            1000 hogtied
            1001 hogtied
            1002 sexandsubmission  (3043)
            1003 whippedass
            1004 sexandsubmission  (3043)
            1005 fuckingmachiens
            1006 sexandsubmission  (3043)
            1007 sexandsubmission  (3043)
            1008 hogtied
            1009 --none--
            1010 sexandsubmission

        There seems to be inconsistent behavior for 404's...  either defaulting to one set, or not
        displaying any thumbnails at all.


This is the indicator for video versus images:

    http://promo.whippedass.com/g/1/4591/i/1/h/
                                         ^ images

    http://promo.fuckingmachines.com/g/1/1086/v/1/h/
                                              ^ videos

    http://promo.fuckingmachines.com/g/1/1086/m/1/h/
                                              ^ images + videos (mixed/hybrid)

The video and image galleries usually come in pairs:

    images: http://promo.fuckingmachines.com/g/1/1086/i/1/h/
    videos: http://promo.fuckingmachines.com/g/1/1086/v/1/h/

    images: http://promo.wiredpussy.com/g/1/1086/i/1/h/
    videos: http://promo.wiredpussy.com/g/1/1086/v/1/h/