Show remote images in Mail.app

Use the following one-line script:

*tell application "Mail" to set download html attachments to true*

Sorry. I misunderstood your question. Here's a script that should do what you are asking for:

--BEGINNING OF SCRIPT
using terms from application "Mail"
on perform mail action with messages theMessages for rule theRule
tell application "Mail"
activate
repeat with eachMessage in theMessages
open eachMessage
tell application "System Events" to tell process "Mail"
if button "Load Images" of front window exists then
click button "Load Images" of front window
end if
end tell
end repeat
end tell
end perform mail action with messages
end using terms from
--END OF SCRIPT

Please let me know if anything doesn't work as expected.