The ornamental design for a decorativepanel, as shown and described.
FIG. 1 is a front perspective view of a decorative panel, showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a right-side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a partially enlarged front view of the portion, I-I′, II-II′, III-III′, and IV-IV′, in FIG. 2.
The broken lines are for environmental purpose only and form no part of the claimed design. The dot-dot-dash broken lines outlining portions of the claimed design that are illustrated in enlargements form no part of the claimed design.