The ornamental design for a baseplate for use with toy pieces, as shown and described.
FIG. 1 is a front, right, top view of a baseplate for use with toy pieces showing my new design;
FIG. 2 is a top elevation view thereof, the bottom elevation view being identical;
FIG. 3 is a front plan view thereof; and
FIG. 4 is a left side elevation view thereof, the right side elevation view being identical; and,
FIG. 5 is a rear view thereof.
The baseplate for use with toy pieces is used to position and support toy pieces, including toy pieces in the form of a toy bricks, over a generated image display surface, including tablet computer screens.