Welcome to the Cesium community @jalibu! Have you tried out the base layer picker widget in the top right? That has an example of a few different imagery layers available from your Cesium ion account, including the “Bing Maps Roads” which is just the roads/features without the satellite imagery:
Thanks Omar for your response.
As a beginner it was difficult to use the right terms for my own question. But your answer helps me a lot.
I would like to represent the globe as abstract as possible (like on my screenshot). No names, no rivers, etc. Just flat, monochromatic continents.
To make my question more concrete: Is there a library with freely available WMTS/TMS imagery in addition to those from the widget?