Recommended sizes for images

Paper Background

Background image that can be tiled or shown in its entirety

1280 x 800 pixels or larger for background image.

No recommended size if image is tiled.

Paper Thumbnail

Image used to represent paper on the paper.li newsstand as well as on social networks

268 x 181 pixels

 Custom ad image (Pro)

Image used in ad space

300 × 250 pixels

 Top Banner (Pro) 

Image or logo shown on top of your paper and on your curated newsletter.

1170 (max width) x 300 pixels 

 Favicon (Pro papers with a custom domain URL)

Short for "favorite icon", displayed by a web browser next to the URL in the address bar, next to the website's name in a list of bookmarks, and in the title page in browsers that have tabbed browsing.

Using .ico format is recommended, which will guarantee that file is converted to correct size. There are many tools on the web that you can use to convert images to favicons.   Here's just one:  Favicon from Pics 

 You must own the copyright or have the necessary rights for any content you upload.