Hi Cere,
Try this
polygon = Graphics[{Black, CountryData["Australia", "Polygon"]}];
maskData = ColorNegate[polygon];
backdrop = Image[Graphics[{Black, Rectangle[{0, 0}, {2, 2}]},
Background -> Black], ImageSize -> {700, 700}];
mask = Image[ImageCompose[backdrop, maskData], ImageSize -> {300, 300}];
text = WikipediaData["frog"];
WordCloud[ToLowerCase@DeleteStopwords@StringTake[text, 1000], mask,
Background -> Black,
ImageSize -> 400,
ColorFunction -> ColorData["SiennaTones"]]
