The ornamental design for an adjustable mirrorstand, as shown and described.
FIG. 1 is a front perspective view of an adjustable mirror stand according to the present invention shown in a first position with a mirror attached thereto;
FIG. 2 is a front perspective view of the adjustable mirror stand shown in a second position with the mirror attached thereto;
FIG. 3 is a front perspective view of the adjustable mirror stand shown in the second position without the mirror;
FIG. 4 is a front view thereof;
FIG. 5 is a rear view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is a right side view thereof;
FIG. 8 is a top view thereof; and,
FIG. 9 is a bottom view thereof.
Portions of the adjustable mirror stand shown in broken lines form no part of the claimed design. The broken line showing of the mirror illustrates the environment of the claimed design and forms no part thereof.