Well, here's the breakdown:
Took the background from Hyrule castle:

It was a little damaged, but I fixed it up in the edit.

Then I edited all Icons into Ganon's pig emblem. The windows depict an abstract pig holding the triforce, but because it's in GBA screen size, you can't see all of it.
And naturally, the throne looked a little too happy, so I fixed that up.

The really hard part was to get Ganondorf to look like the Minish Cap sprites. Thing is, he's big, has a tiny head and a lot of black on him were as most of the original sprites have huge heads, tiny bodies and bright colours.
This is a far as I can light them up before his orange patters start to fade. I'm still a little unsure about the result, but.. meh.

And of course, the finished thing.
Hope more people join in.
(Heh, bastard.)