I claim the ornamental design for an upholstery material, as shown and described.
FIG. 1 is a perspective view of an upholstery material, showing my new design;
FIG. 2 is a front elevational view thereof, the rear elevational view being a mirror image thereof;
FIG. 3 is a left-side elevational view thereof, the right-side elevational view being a mirror image thereof;
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a bottom plan view thereof.
The broken lines showing additional upholstery material in the figures depict environmental matter and form no part of the claimed design. The upholstery material is shown with a symbolic break in it length and width. The appearance of any portion of the article between the break lines forms no part of the claimed design.