Does it work in Safari in the Mac? I tested it there but no joy (Safari 6 on 10.8) I've been struggling with Safari myself - it only allows you to catch paste events if the user is pasting into a text box - unlike Chrome which lets you catch paste events no matter what HTML element type catches them. I think google docs works around this by having an invisible text box capture & re-direct interaction events.
Pasting in Safari doesn't quite work, like you said the paste event requires a text box to trigger, and while it seems to have the same clipboard API as Chrome, images don't seem to show up there.
In Firefox a contenteditable div is used to catch pasted content, when images are pasted an img tag with base64 encoded image data is inserted, which is easy to just grab and display. Unfortunately, this doesn't work in Safari.
Because Safari seems to support all the needed APIs, it's hard to detect and inform the user that copy and paste doesn't work. I'd rather not do any browser sniffing.
