The ornamental design for a signframe, as shown and described.
FIG. 1 is a front, top, and left perspective view of a sign frame in accordance with the present disclosure;
FIG. 2 is a left side view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a front elevation elevation view thereof;
FIG. 5 is a back elevation elevation view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a front, bottom, and right side perspective view thereof.
In the drawings, the broken lines depict unclaimed subject matter only and form no part of the claimed design. The separation and brackets indicate that the precise length of the sign frame is not claimed.