fyi, did some quick testing (I was also curious about image dragging):

Pale Moon 27.9: Image conversion to base64 worked perfectly

Dooble 1.50: creates clickable link (file:///home/user/.../filename.jpg)

Midori 0.5.11: creates NON-clickable link

Otter 0.9.09 beta 9: creates clickable link

Chromium 65.0.3325.181: opens new tab

Opera 45.0: opens new tab