There are many options to show data, and you really do not have to limit yourself with those which are bundled with KNIME. In the community contributions (http://tech.knime.org/community), there are many options available. We will cherry-pick some of the more general and interesting visualization nodes.
The R plot, Python plot, and Matlab plot are available from the corresponding scripting extensions (the KNIME R Scripting extension, KNIME Python Scripting extension, and KNIME Matlab Scripting extension) on the community nodes update site.
The usage of these nodes do not require experience in the corresponding programming languages. There are templates from which you can choose and the parameters can be adjusted using KNIME controls. Obviously, you can create your own templates or fine-tune existing ones if you are not satisfied.
You need to have access to (possibly local) servers to connect to the extensions. (The Python Plot...