Tip of the Day Plus is a great little app for sharing information on your SharePoint site. As well as tips it is flexible enough to be used for presenting any information on your site (e.g. Myth of the Month, Article of the Week, etc.).
There is an admin centre where multiple lists can be configured to store your tips. You can configure the App Web Part to display the latest entry, or select a random entry. There is a default tip image, but you can also use your own.
There is also functionality to allow you to apply your own styling via CSS.