User blog comment:~Boggy B~/New Background/@comment-7697305-20150307220053

Do you happen to still have the image at its original size? If so, then you may be able to reduce the file size by slightly reducing the image quality rather than majorly reducing the image size.

As an example of what I mean, compare to. They basically look identical (and are the same resolution), but the former is 1.36 MB (1360 KB) while the latter is 295 KB.