The ornamental design for a motorcycleseatcoverassembly, as shown and described.
FIG. 1 is an exploded right elevation view of a motorcycle seat cover assembly showing my new design, the opposite side being a mirror image of that shown;
FIG. 2 is a rear elevation view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof; and,
FIG. 6 is an isometric view thereof.
The broken lines in FIG. 6 of the drawings depict environmental subject matter only and form no part of the claimed design.