Expert: Keith H. Patton - 10/28/2009

Question
is there a language to how the horses are posed?  ie;  one leg up meaning something,  reared up meaning something,  etc

Answer
Yes.  Popular belief is that if the hose is rampant, or rearing, with two legs in the air, the rider died in battle.  If one leg is up, he was wounded in battle or died of his wounds.  If all four legs are on the ground, he died of natural causes other than combat.  

According to wikiepedia, These rules apply to the battle of Gettysburg but even that relationship is coincidental.  It could prove to be an interesting project to determine how often this supposed convention actually holds true.  In Europe statues do not seem to conform.
From my visits to Civil War battlefields, I see a slight correlation.  But that might be due to the fact that most of the statues at these battlefields were erected in the late 1800's and early 1900's by a hand full of foundaries across the country.  There might have been some unwritten agreement between the sculptors on this point.