When the image size, the image file size, the resolution of the image, and so on are large, an error like Request Too Large occurs. In this sample script, such the image can be converted to Google Document by reducing them.
Here is a workaround for converting large images to Google Docs from Kanshi Tanaike. The post includes a code snippet and link to related Stack Overflow Q&A. As noted in the SO discussion the solution might be a compromise for some developers as it reduces the image resolution being passed into Google Drive and if you need to keep the original quality you might have to look at other paid services.