You can make anything you want with the paintbrush tool or the pen tool. The pen tool is particularly useful for making very precise perfect curves like the arches or curvy lines you mentioned.
I guess everyone kind of assumed it was supposed to be a for-profit product, as it was mentioned that the author was intenting to make a "print" version of it. :D
Actually, international copyright law still applies, even if it's given away for free. They probably wouldn't sue you or anything, but they could send seize and desist letters at any time, demanding that the project be stopped.
Even though I like Zelda, this is just blatent copyright infringement. It may pass unnoticed if it's given out for free, but I sure hope you are not planning on selling it.
Wish can only give you what is listed in the spell description, which I am fairly certain does not mention repeling demon invaders. Perhaps you are thinking about 2nd edition, where the spell was much more powerful.