This feature request is now in the planning stage. As more details become available, I will post them here.
As we announced at Microsoft Ignite 2019 this morning, we are excited to confirm that Multi-window capabilities are coming to Microsoft Teams, and will start rolling out to the public ring early next year!
Alex & the Teams team
You should experience significant improvements in copy & paste of images within Teams, as well as to & from Teams. We are aware of a few remaining issues, but the most common cases are resolved.
Thanks again for your patience on this one.Chris Bardon commented
I noticed that this still isn't working in the current build. Copy/paste shows the image in my chat view, but it doesn't appear for others, and disappears if I navigate out of the channel and back.