The ornamental design for a rear crownpanel, as shown and described.
FIG. 1 is a front perspective view of the rear crown panel showing my design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a rear perspective view of a cap incorporating my design.
The broken lines in FIG. 8 are for the purpose of illustrating the environment in which the design is associated and form no part of the claimed design. The remaining broken line subject matter represents unclaimed features.