The ornamental design for a cornerpictureframe, as shown and described.
FIG. 1 is a perspective view of a corner picture frame showing my new design.
FIG. 2 is a top plan view thereof;
FIG. 3 is a left side elevation view thereof;
FIG. 4 is a front elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6: is a rear elevation view thereof;
FIG. 7: is a bottom plan view thereof; and,
FIG. 8: is an exploded perspective view showing multiple frames stackable on top of each other.
It is to be understood that any portion of any figure shown in broken lines are for environmental purposes only and form no part of the claimed design.