Currently only plain text can be synchronized from Drafts folder.
Any Rich Text or image cannot be synchronized from Drafts folder to mobile device. This limitation is documented at following link.
Mail synchronized to the Drafts folder on the device loses formatting.
When mail is synchronized to the Drafts folder on the mobile client, the content is synchronized as plain text. Any rich text formatting within the document is not included. Editing the draft content on the device and/or sending the mail removes any formatting from the mail document. Use HCL Notes, HCL iNotes, or HCL Verse web clients when editing or sending drafts.
So there is a feature request to add the Rich Text and image support for Drafts mail, so that mails can be later edited from mobile devices and user can sent it from anywhere. This Enhancement Request is submitted for Traveler V11 and V12