The ornamental design for a cover for an illuminationdevice, as shown and described.
FIG. 1 is a perspective view of the cover for an illumination device of the present invention;
FIG. 2 is a front elevation view thereof, the rear, right side, and left side elevation views being identical thereto; and,
FIG. 3 is a top plan view thereof.
The evenly spaced broken lines shown in the drawings are directed to environment, are for informational purposes only, and form no part of the claimed design.
The surface shading lines are provided only to indicate the character and/or any contour or curvature of the surfaces. They do not indicate color, texture, markings that actually exist thereon, indicia, graphic representations, surface treatment, or any other ornamentation applied to the article.
The oblique line shading is present to show the translucent nature of the surface.