@ Chitra: No, you are not supposed to attach any public images or copyrighted picture or water marked picture in this site. However, if you are writing about a product or item in this site, you may use the pictures posted in the original manufacturer's website of the product / item and no other picture is allowed. Otherwise you may post your own picture taken in your camera.
@ Mridula: Points and Cash credits are completely different. Cash credits are given directly to your credit depending upon the web traffic worthiness of your contributions and cash credits may vary depending upon the topic you write. Points are awarded depending upon many factors including the size, images, traffic worthiness etc. So, points can't be converted in to Cash credits and both are completely different.
Thanks & Regards -