You would have to create a custom data type (which lives in the Lists table of the core). This custom data type would more than likely have to reference an assembly, class with your logic to handle such things. When doing this you are getting into things w/ the lifecycle of hte page and you can find yourself scratching your head wondering why something isn't working. The short answer to your question is this is possible, but probably not very easy to do as is. No matter what you need to find a way to get the image from the user to the server which requires some upload mechanism.

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