The ornamental design for a massageboard, as shown and described.
FIG. 1 is a top-left-front perspective view of the massage board showing of my design;
FIG. 2 is a bottom-right-rear perspective view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a front elevational view thereof;
FIG. 6 is a rear elevational view thereof;
FIG. 7 is a left elevational view thereof;
FIG. 8 is a right elevational view thereof;
FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 3; and,
FIG. 10 is a top-left-front perspective view of the massage board with cushions attached.
The broken line showing of attached cushions in FIG. 10 is included for the purpose of illustrating environmental structure and forms no part of the claimed design.