Excellent software for mapmakers

[Agrajag]

You could also use the HoMM II map editor and random map generator, if you can't get the HoMM III one.
(I also suppose that if you intend to buy it, HoMM II will be cheaper than getting HoMM III Complete).

And besides, all the Hardcore HoMMers know that HoMM II is the best game, while HoMM III is merely the most popular one.

BTW, you could also use the Warlords: Battlecry II/III map editor, it has nice blending effects and quite large tiles.