The ornamental design for a back cover for mobiletelephones, as shown and described.
1. Back cover for mobile telephones
1.1 : Rear view of the back cover for mobile telephones, showing the sliding camera covering in a closed condition and the stand feature in a relaxed condition
1.2 : Second rear view thereof, showing the sliding camera covering in an open condition and the foldable stand feature in a folded condition
1.3 : Rear, right side perspective view thereof, showing the sliding camera covering in a closed condition and the stand feature in a relaxed condition
1.4 : Second rear, right side perspective view thereof, showing the sliding camera covering in an open condition and the foldable stand feature in a folded condition
1.5 : Rear, left side perspective view thereof, showing the sliding camera covering in a closed condition and the foldable stand feature in a folded condition