Lol, yes I'm sure the file exists.
I've tried that and it runs without errors in the debugger, but doesn't paste the image in mail. It does work in other apps though, so unless it's fixed in either an Apple or Alfred update I guess it just won't work.
With regards to running a snippet that calls the image paste workflow, I've never managed to get that to paste the clipboard. When I say "returns" I mean that the snippet calls the workflow because I'm using ;emailsignew in the snippet, but it just shows the text ";emailsignew" instead of pasting the clipboard.