You have very little upper body rotation on your serve. It's mostly an arm serve. You are also more likely to injure your shoulder from your upright hitting posture. To improve your UBR, you must incorporate shoulder "turn & tilt" at the peak of the toss so that your upper body can rotate toward the target adding body mass to your shot.
Imagine a tennis ball can tilted back and rotating back and forth. That what your upper body should be doing on serve. Like a golf swing except your spine is tilted back instead of foreward. To accomplish this, at the peak of the toss, your back should be 3/4 to the target. That's the turn. If you have your name across your shoulder blades, your opponent should be able to read it. At the same point in time, your left shoulder should be as high above your right shoulder as comfortably possible. That's the tilt. This will also automatically put you in a position to naturally swing up to the ball giving your ball flight a nice arch with lots of topspin.
At present, you have almost no shoulder turn and tilt, and therefore, almost no UBR, ala Jimmy Connors. Your side is to the target and your shoulders are nearly parallel to the ground at the peak of the toss.
Hope this helps.
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