The ornamental design for a lightingfixturebackplate, as shown and described.
FIG. 1 is a right side elevational view of the lighting fixture backplate
in accordance with the design, illustrated in an environment of a lamp,
the left side being a mirror image thereof;
FIG. 2 is a front side elevational view of the lighting fixture backplate
in accordance with my design;
FIG. 3 is a rear side elevational view of the lighting fixture backplate in
accordance with the design; and,
FIG. 4 is a bottom plan view of the lighting fixture backplate in
accordance with the design, the top side being a mirror image thereof.
The broken lines show the environment in which the article is used and are
not considered part of the design claimed.