The ornamental design for a paintingstand, as shown and described.
FIG. 1 is a top, front, left side perspective view of a painting stand
showing my new design; and,
FIG. 2 is a top, front, left side perspective view of an alternate view of
the embodiment of FIG. 1, the bumper is shown in broken lines for
illustrative purposes only and forms no part of the claimed design.