The image downloads because it's being served with this header:
content-disposition: attachment; filename="apps_icons.png"
I imagine Google made it like that to avoid exactly what
@AnandGupta tries to do. They clearly don't want people to use their servers as remote image storage, eating bandwidth and resources for no actual Google benefit.
Realistically? Nothing much, change provider.
By over-engineering it? Setup your own proxy that requests the image from Google and then serves the image to the forum without that header. (But it would a lot easier to just serve your image from the proxy server
)