One of the Oddest Post Cards Ever

From the Cooper Postcard Collection, MDAH

This one has me completely mystified as to intentions.  It is a photograph of a riderless horse, (or perhaps a mule or hinny) in a cemetery in Silver Creek, MS.  The caption to the left reads, "Write Me a Cheerful Letter Quick. Silver Creek, Miss."  I cannot tell if the whitish blotch over the saddle is just age and discoloration or if someone attempted to alter the photo to make it appear a ghost is in the saddle.  

The date is estimated to be in the late 1800s or early 1900s.