The ornamental design for a storagebox, as shown and described.
FIG. 1 is a front view of the storage box in an open configuration, showing my new design;
FIG. 2 is a front view thereof in a closed configuration;
FIG. 3 is a left side view thereof in an open configuration, the right side view (not shown) being a mirror image of the left side view;
FIG. 4 is a left side view thereof in a closed configuration, the right side view (not shown) being a mirror image of the left side view;
FIG. 5 is a bottom view thereof in an open configuration;
FIG. 6 is a bottom view thereof in a closed configuration;
FIG. 7 is a top view thereof in an open configuration;
FIG. 8 is a top view thereof in a closed configuration;
FIG. 9 is a rear view thereof in an open configuration;
FIG. 10 is a rear view thereof in a closed configuration; and,
FIG. 11 is a perspective view thereof.
The broken lines immediately adjacent the compartment interiors in FIGS. 1 and 11 represent the bounds of the claim. The remaining broken lines illustrate portions of the storage box. None of the broken lines forms part of the claimed design.