This is one of my designs that I'm really happy with, probably just because I feel the colors go together really well while being arranged in a very distinct manner. I don't remember what I had in mind symbolism-wise when I made this flag, but here are my guesses:

• The pine is a prominent symbol of New England.
• The triangular arrangement of the colors represents New Hampshire's nickname, the White Mountain State. You can even view the white and yellow triangles as a white, shaded mountain.
• The white & red allude to England's flag (more New England symbolism).
• The blue & yellow were probably taken from the original flag using symbolism from the seal, with the blue evoking the water from the harbor and the yellow representing granite (New England also being called the Granite State).