The ornamental design for a christmastreestand, as shown and described.
FIG. 1 is a front elevational view of a Christmas tree stand showing our new design;
FIG. 2 is a right side elevational view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a rear elevational view thereof with an access door open;
FIG. 7 is a right side elevational view thereof with the access door open; and,
FIG. 8 is a top plan view thereof with the access door open.
A Christmas tree shown in broken outline in FIG. 1 is for illustrative purposes only and forms no part of the claimed design. Portions of the Christmas tree stand shown in broken lines form no part of the claimed design. All sides not shown form no part of the claimed design.