Customized torch/flash light using a perfboard with an attiny
As Ignacio said - the outer case of the torch supplies the -ve connection from the battery. 
You need to supply a connection for circuit-negative to the case at the edge of the perf board



The current drive capability of an ATtiny85 is not very large and will not drive an LED very brightly. If the result you get is acceptable then move current drive may not be needed. You do not say what battery voltage you are using but if it is say 3 x AAA batteries then adding a current buffer is not hard but can be challenging. Ask about thi if of interest.

All unused I/O pins of the ATtiny85 must be dealt with properly to avoid problems. Either set pins to output, or set them to inputs and connect to ground or Vcc (ideally via a resistor. Any of these option avoid having the pins float in a high impedance state with a possibly unexpected effect on circuit performance.