The ornamental design for a tuning peg cover, as shown and described.
FIG. 1 is a first front perspective view of a tuning peg cover, where the rear perspective view of the tuning peg cover is a mirror image of the first front perspective view;
FIG. 2 is a front view of the tuning peg cover, where the rear view of the tuning peg cover is a mirror image of the front view;
FIG. 3 is a bottom view of the tuning peg cover;
FIG. 4 is a top view of the tuning peg cover;
FIG. 5 is a right-side view of the tuning peg cover, where the left-side view of the tuning peg cover is a mirror image of the right-side view;
FIG. 6 is a cross-section view of the tuning peg cover taken in the direction of line 6-6 of FIG. 2; and,
FIG. 7 is a second front perspective view of the tuning peg cover shown with environmental subject matter.
The broken lines shown in FIG. 7 depict environmental subject matter that forms no part of the claimed design.