FIG. 1 is a perspective view of an illumination device showing our new design, with the illumination device's base shown in broken lines for illustrative purposes only so that it forms no part of the claimed design:

FIG. 2 is a front elevational view thereof, with the illumination device's base shown in broken lines for illustrative purpose only so that it forms no part of the claimed design;

FIG. 3 is a top plan view thereof;:

FIG. 4 is a left side view in elevation thereof, with the illumination device's base shown in broken lines for illustrative purposes only so that it forms no part of the claimed design;

FIG. 5 is a rear elevational view thereof, with the illumination device's base shown in broken lines for illustrative purposes only so that it forms no part of the claimed design;

FIG. 6 is a right side view in elevation thereof, with the illumination device's base shown in broken lines for illustrative purposes only so that it forms no part of the claimed design; and,

FIG. 7 is a bottom plan view thereof.