Putting things together was straight forward. I took the code from Adafruit: Multi-tasking the arduino part 2 which I modified for 1 servo and 1 LED only. Moreover, since I use an ATtiny85, I had to call the SoftServo library instead of the normal servo library.
I soldered two red LEDs in parallel and added a suitable resistor in series. I was not sure how much output the Attiny would deliver, so I added a BC547 to drive the LEDs.
I connected the LEDs to one pin of the Attiny, the servo to another and put all onto a small piece of perfboard. The circuit being so simple I didn't care to draw a schematic. To illuminate the head which turns back and forth a bit, I added a white LED with a suitable series resistor.
Everything is driven from 5V. For some reason my supply voltage was not sufficiently stable anymore at the Attiny (the servo stopped moving after one or two cycles), so I added a 100uF cap for stabilisation.
To mount the skeleton to the servo I designed and printed a small adapter.