C4D has an upper limit of 16000 pixels in both directions, but a still image, at that size, will take a very long time to render, on a single machine.

Here is the link to a tutorial on setting up a "Tiled Camera" for rendering large stills, in C4D.

https://www.youtube.com/watch?v=rx1F9xAXI10

This tutorial shows you how to break a single-frame into "Tiles". Each tile can be rendered on a separate render-node, allowing multiple render-nodes to work in parallel, on all the tiles.