"Summary: A user’s understanding of an icon is based on previous experience. Due to the absence of a standard usage for most icons, text labels are necessary to communicate the meaning and reduce ambiguity."
"There is no need to translate icons for international users, provided that the icons are mindful of cultural differences (for example, mailboxes look very different in various countries whereas envelopes look the same, therefore an envelope is a more international icon for an email program than a mailbox)."
And hey what do you know, good ol' NN/g released an article to help my case.
http://www.nngroup.com/articles/icon-usability/
Specifically for this case:
"Summary: A user’s understanding of an icon is based on previous experience. Due to the absence of a standard usage for most icons, text labels are necessary to communicate the meaning and reduce ambiguity."
"There is no need to translate icons for international users, provided that the icons are mindful of cultural differences (for example, mailboxes look very different in various countries whereas envelopes look the same, therefore an envelope is a more international icon for an email program than a mailbox)."