Templates

Online Image Editor includes it's own proprietary image format (.oie) that stores all layer and graphical elements information. You can create a 'template', e.g. a banner with 'type your companyname here'. When the customer opens that template in Online Image Editor they can replace the text with their own and preserving all the other layout elements. They then would upload the image to server (as jpg, png or gif) or save it on their own local machine.
A template can consist of an unlimited amount of elements or layers, layers can be 'locked' to prevent distorting the actual design. A user would be able to change the text in the template, but not move the text to a different location in the design.