For example, in this image you would want to change the size when erasing between the petals. For example, drawing a line from top to bottom will have the pattern start at the top and finish towards the bottom as the image with a pink background demonstrates. In the Layers panel, drag the background layer below the foreground image layer.
Right at the bottom there, Background Contents. Well, other than the lighting being atrocious and the photographers being underpaid civil servants, bad photos usually result from bad backgrounds. Dont forget the foreground and background color blocks over on the left under the toolbox. Focus on erasing on the exact edge of the subject. Switch your plain white stand-in background for a more vibrant one by watching this Photoshop tutorial on how to change your background. Arrays of three are flexible to set up - vertical stack for long throw, horizontal array for short throw applications. To accomplish what you want to do I think the best approach would be to use the Magic Extractor Tool. Use different selection tools to paint over the image youd like to keep.