Images should only be uploaded into the content folders. Never upload any images (or files) into the Page Layout set of folders.
Image file names that contain punctuation, such as commas or apostrophes, will not show up properly on the website.
Be certain the file name does not contain commas, apostrophes, etc. before uploading the image. Avoid spaces in file names as well. Use a dash - or underscore _ in place of spaces.
Using the Save for Web option compresses the image file for faster performance.
Upload the image to the CMS library as normal, either directly into the library or by placing it into a webpage or into a news post.