Sprite Stitch Board!

So, it's my dad's birthday and I know he'd like this particular stitch.


I can't figure out a good size, and I don't care about the detail on the death star, at least not the minor details.
If I could get some help on this, that'd be great. I've got 14ct black currently, so that's what I'll use.

I'm open for ideas on sizing and things. I'd like the rainbow to be much more vibrant than this picture has it.

Hello Schutzenegger !
Your dad have great music tastes !

Here is the second pattern I made (the first one was 450 x 450 stitches, I thought it was too huge...)
This one is 250 x 250 stitches (I cut it in half because all the rest is black stitches ; you should let almost 60 rows of black stitches above and below the pattern...
With your black 14ct aida, it would be 17,9 inches (45,4 cm) height and length ; would it fit ?
Ho, and I'm not sure of the #939 color, it's a dark marine blue in reality, I almost don't see the difference with the black #310 ; and on KG chart #939 appears as a dark brown (?). I don't know if you'll have better contrast with black aida, than with #310 thread... you should test it before...