Plate element for a construction set

FIG. 1 is a top perspective view of my ornamental design for a plate element for a construction set;

FIG. 2 is a top plan view thereof;

FIG. 3 is a front plan view thereof;

FIG. 4 is right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a back side view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines in FIG. 7 are for environmental purposes only and form no part of the claimed design.