The ornamental design for a decorative cornerblock, as shown and described.
FIG. 1 is a perspective view of a decorative corner block according to the present invention;
FIG. 2 is a front view of the decorative corner block of FIG. 1;
FIG. 3 is a right side view of the decorative corner block of FIG. 1, the left side view being a mirror image thereof;
FIG. 4 is a back side view of the decorative corner block of FIG. 1;
FIG. 5 is a top view of the decorative corner block of FIG. 1; and,
FIG. 6 is a bottom view of the decorative corner block of FIG. 1.
The broken lines in FIGS. 1-3 immediately adjacent the solid lines represent the bounds of the claim, and the broken lines and the area within the broken lines represent unclaimed portions of the present invention. None of the broken lines form a part of the claimed design.