I am trying to upload an image. However I believe I have stepped over the file limit. What puzzles me is that it was a relatively simple test render with only a tree, two 2 planes, and two lights. I have sampling set to 30. But for some reason the file size is over 2 MB and it is a PNG. What am I doing to make this so large.
Use a higher compression ratio. PNG uses a lossless compression algorithm, so no need to be shy. In addition to that: Can you lower the resolution?
And for the record: The size of an image file does not really depend on the subject it shows. In the end a pixel is a pixel, regardless of what colour it has (there are exceptions, though, if the image contains large unicoloured areas, which compress very nicely in PNG).