No, unfortunately, you cannot copy and paste an image. You will need to either link to an image URL or download the image locally and then upload it via the Photos button on the toolbar.
The vendor that we works with uses this workflow to allow some companies to provide image moderation before communities get spammed. We do not currently moderate images, but I'm afraid we still need to go through the same workflow. We've made a recommendation to the vendor to improve this feature going forward.