Lider1,
Well, firstly, there are very few new maps there, as almost no one plays the fourth installment. Secondly, many of them are either in a language I don't understand or are of size S-M and can be completed in a couple of hours, even if you fully explore them and clear them of all neutral creatures. And thirdly, I've already searched many websites, including this one, and downloaded all the maps that caught my eye. Sometimes I still look for new maps, but rarely find anything that is really worth playing.