The ornamental design for a brush handle, as shown and described.
FIG. 1 is a perspective view of a brush handle showing our new design;
FIG. 2 is a front side view thereof;
FIG. 3 is a back side view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a bottom view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a perspective view shown in condition of use.
In FIGS. 1-8, the broken lines are for purposes of illustrating portions of the brush handle, which form no part of the claimed design. The additional broken lines in FIG. 8 depicting a hand are to show the environment of use and form no part of the claimed design.