The ornamental design for a mountingdevice for pictures, as shown and described.
1. Mounting device for pictures
1.1: Front perspective view
1.2: Rear perspective view
1.3: Side plan view
1.4: Front plan view
1.5: Rear plan view
Fig. 1.1is a front perspective view of the mounting device for pictures; fig. 1.2is a rear perspective view thereof; fig. 1.3is a side plan view thereof; fig. 1.4is a front plan view thereof; fig. 1.5is a rear plan view thereof.