We claim the ornamental design for a seat support cover, as shown and described.
FIG. 1 is a perspective view of a seat support cover on a stool showing a back, a right side and a portion of a top.
FIG. 2 is another perspective view showing a front, the top and a left side of the seat support cover of FIG. 1.
FIG. 3 is another perspective view showing the front, the bottom and the right side of the seat support cover of FIG. 1.
FIG. 4 is a left side elevational view.
FIG. 5 is a front elevational view.
FIG. 6 is a top plan view; and,
FIG. 7 is a bottom plan view.
The broken line showings of internal and mounting portions of the seat support cover form no part of the claimed design. The broken line showing of a portion of the stool illustrates the environment of the claimed design and forms no part thereof.