The ornamental design for a lamp with a decorativefaceplate and prismatic housing, as shown and described.
FIG. 1 is a left side perspective view of the lamp with decorative faceplate and prismatic housing showing a first embodiment of the new design, with the right side being a mirror image thereof;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof; and,
FIG. 4 is a series of bottom plan views showing obvious alternate forms of the decorative faceplate portion of the design.
The broken lines shown on the drawings are for illustrative purposes only and form no part of the claimed design.