I've only just started Cover Crazy, so here is my first one...
• The white background. It helps focus the observer's eyes to the main object of the cover. In this case, it is the title.
• That splash of colour, literally. Since there is such a plain backdrop, you have to rely on the colourful factors to make a good first impression.
• The cover suits the plot very well, as it's about a young boy who has only lived in one room for his whole life. Thus, the empty looking cover page.