Pomeroy's story has all the makings of a good folk hero tale — he was a frontier gunsmith who took part in the Louisbourg expedition, fought at Lake George during the Seven Years' War, and, at age 69, rode 100 miles in a night to help defend Bunker Hill. He kept journals — there's even a poem about him. Seth Pomeroy would be a good character for historical fiction — he was everywhere and he seems to have been a bit eccentric.
The sources indicate that Pomeroy is not actually buried in Northampton. He fell ill and died in Peekskill and was buried in an unmarked grave. I haven't been able to find any mention of his body being relocated, so I suppose the monument in Northampton is a cenotaph.
The imagery is interesting, too. The "CSP" stands for "Colonel Seth Pomeroy," but I have no idea what the "BG" on the little flags might mean. Guesses?