The ornamental design for a shell for washingmachine, as shown and described.
1.1 is a front view of a shell for washing machine showing our new design;
1.2 is a back view thereof;
1.3 is a left view thereof;
1.4 is a right view thereof;
1.5 is a top view thereof;
1.6 is a bottom view thereof;
1.7 is a perspective view thereof; and
1.8 is another perspective view thereof.
The interior features which are only visible through the openings in the shell for washing machine in Figs. 1.2 and 1.6 form no part of the claimed design.