Does anyone have any pointers on how to use AppleScript to create a
new image item in Yojimbo?

Using Applescript to make a new note item in Yojimbo is fairly easy
with something like

set itemContents to the clipboard contents
tell application "Yojimbo"
set newItem to make new note item ¬
with contents itemContents
end tell

Replacing the third line in the above code with

set newItem to make new image item ¬

yields

error "Yojimbo got an error: AppleEvent handler failed." number
-10000

IÂ’m stumped and looking for some pointers.