FIG. 1 is a perspective view of a seat design; FIG. 2 is a top elevational view thereof; FIG. 3 is a front elevational view thereof; the backside being a similar image thereof; FIG. 4 is a bottom image thereof; and, FIG. 5 is a left side elevational view thereof; the right side being a mirror image thereof. The broken lines are for illustrative purposes only and form no part of the claimed design.