It would be fantastic to have the ability to pull a private image with the Dockerfile during the image-building process on Render.
This would allow me to utilize a base image and significantly reduce the build time.
Here's an example Dockerfile illustrating the concept:
```dockerfile
...
COPY app .
CMD run app
```
By incorporating this functionality, Render would empower users to optimize their builds by leveraging pre-existing private images as a foundation for their projects.