I'm using the Billboard cesium class in order to place a picture on Earth. This I can do, no problem.
However, I want it to be static, I mean that if you rotate the Globe or zoom in, the picture doesn't update position and remains fixed in space, not attached to how you move the Earth's view.
Billboards are made by design to always face the viewer. I think instead you may want to create a polygon, and attach a texture/image material to that polygon. That way it won’t move when the camera moves.
Well, What I meant was that if the image or billboard could remain in the same position of the screen!, like a button that doesn't change position so it is independent of the camera and independent of the translation in space.
I think in that case you might be better off creating an HTML element on top of the canvas (so it’s outside of Cesium). This is how the widgets and the timeline work for example.A lot of the examples on Sandcastle (https://cesiumjs.org/Cesium/Apps/Sandcastle/index.html) have buttons added on top just directly in the HTML like that.