I got it to work with Chrome but only because I had the image hosted on Tumblr already.
What I did after uploading my picture privately on Tumblr (yes that is a thing you can do) was this;
- Enlarged the image and right-clicked to select "Copy the image WEBADRESS" (not just the picture)
- Then return to Tapas and enter edit mode.
- Then pick the spot for the image and hit right-click on your mouse.
- Select the option "Paste"
Then the picture should show up.