LOL Skippy! does the SAME victory dance thing!! And i called it the same thing as you, a victory dance!! After we did a lesson (an hour of flat work, i dont jump him, i trained him in lower level dressage instead) i would let him pick any jump in the arena to go over however he pleased.
He would then usually pick the smallest flat jump (like an Oxer i guess?) a flat pole that was a foot off of the ground. He would pick up this HUGE canter and just CLEAR it by some 3 feet and come off of it crow hopping and cantering.. he was SO proud of himself LOL any other jump he did after that first one was done with form and beauty, but the first one is ALWAYS "Skippy!'s Jump" LOL
That is so awesome that you see the humor and fun in it, and dont automatically think he is misbehaving.. you have awesome horsemanship! =)
Again, that picture is TOO cute! Im so glad you were able to get that moment captured!