I imagine this as a megaphone (because this draws attention to the message). Here's what I drew but I'm not sure about the color...
for 300 reports
for 1000 reports
for 5000 reports
for 300 reports for 1000 reports for 5000 reportsThis looks good as well, it seems there are plenty of good icons to choose from now.
Would have been nice if the community could have voted for it, once a subset of images has been selected.