The ornamental design for a skateboarddisplayrack, as shown and described.
FIG. 1 is a left lower perspective view of a skateboard display rack illustrating my new design;
FIG. 2 is a right side view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a rear view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is a right lower perspective view of the skateboard display rack of FIG. 1 hanging on an exemplary wallboard and displaying a plurality of exemplary skateboards; and,
FIG. 9 is a left lower perspective view of the skateboard display rack of FIG. 1 displaying a plurality of exemplary skateboards.
All dashed lines are for environmental purposes only and form no part of the claimed design.