Yes, you can have each pin twinkle one LED. Using a higher voltage power source and a transistor for switching you can have each pin twinkle a set of multiple LEDs. If you spread the members of the set over a wide area it should not be obvious that several are blinking synchronously.
Using multiplexing you can have N pins control (N/2)^2 LEDs (50 pins = 625 LEDs). You will need N/2 drive transistors.
Using Charlieplexing you can have N pins control N^2-N LEDs (50 pins = 2450 LEDs). You will only be able to light one at a time.