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.
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.
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