The ornamental design for a boatseataccessorystand, as shown and described.
FIG. 1 is a perspective view of a boat seat accessory stand;
FIG. 2 is a side view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a top view thereof
FIG. 6 is a bottom view thereof;
FIG. 7 is a perspective view thereof with an attached umbrella; and,
FIG. 8 is a perspective view thereof with an attached umbrella and secured to a boat.
The broken lines in FIG. 6 form no part of the claimed design.
The broken lines in FIG. 7 and FIG. 8 are included for the purpose of illustrating the environment in which the article resides and form no part of the claimed design.