I’m all about this concept. I did a project in school that incorporated a skatepark into the campus of a corporation I invented. The company was a clothing/pads/accessories manufacturer, and the skatepark was located in a central courtyard and acted as their proving ground.
There were different means of circulation for the employees and skaters (with some overlap); the skate park was sunken below the grade of the courtyard (with the exception of half and quarter-pipes) and there was a pedestrian bridge that crossed over it and could also act as an observation deck. It would also be visible from the surrounding buildings where the clothing was designed and manufactured.
To discourage the benches meant to be sat on by the employees on break from being commandeered by the skaters, they were made in materials, forms, and dimensions that made them unappealing to skaters as skateable objects, but usable as furniture (I’ve attached some images from said project).
But enough about that. Looking at your image, it seems like you do a good job of making the skaters physically, but not visually, isolated from passers-by… with the exception of the shelter area. If those picnic tables aren’t bolted down, they’re going into the skatepark. If they are bolted down, they’re going to be skated where they sit. If that’s meant to be a neutral zone, I would suggest both bolting them down and surrounding them with some sort of barrier, and making sure the area enclosed is too small to get up to speed in. That being said, it wouldn’t be a bad idea to have movable obstacles such as picnic tables, benches, boxes, and rails, etc…
I would also point out that the plants in the center of the faux-bench/planter are not likely to survive. A properly executed blunt or board slide on the back of the “bench” would take out the front of the border, and everything else is susceptible to somebody bailing into them. Also, these plants probably need irrigation, and sprinkler irrigation and concrete skateparks don’t mix. Maybe if you had drip irrigation and the plants/trees behind (again) some sort of barrier.
To make a more general comment, I don’t think that integrating skatepark design into landscape architecture necessarily means putting plants in a skate park (not that it couldn’t or shouldn’t be done, and not to assume that was your implication). I personally consider skatepark design to be a specialization within landscape architecture, not a distinct discipline. Either way, what we’re talking about is designing a space meant to perform a function.
In closing, this looks like a decent park with several good lines and a nice counter-clockwise flow, but I do feel like it would be nice if that entire lower left-hand edge were a quarter-pipe, and maybe there were another quarter pipe or larger roll-in at the upper right corner.
Here’s an example of something I did in school. Use breaks in mono-cultures to drop shadows and show height. Fields of grass reveal their stalks when they are blown sideways by the wind, and the wind can create eddies of swirling patterns which can be represented in plan. Within a larger monotonous expanse, you can “stipple” with simple plants symbols, and/or splashes of color to represent flowering plants. I also find color blending useful in creating variety.