The ornamental design for a topshelf for flatscreen televisions, as shown and described.
FIG. 1 is a front left perspective view showing my new design.
FIG. 2 is a rear left perspective view.
FIG. 3 is a top view.
FIG. 4 is a left view.
FIG. 5 is a right view.
FIG. 6 is a front view.
FIG. 7 is a bottom view; and,
FIG. 8 is a rear view.
The broken lines in the drawings illustrate portions of the top shelf for flat screen televisions that form no part of the claimed design. The break lines shown in FIGS. 1-8 of the claimed design indicate that the appearance of any portion of the article between the break lines forms no part of the claimed design.