How to implement a pic server?

[eluser]rogierb[/eluser]
So is it safe to say the servers are on different locations or at least not connected to each other? That would have made things a lot simpler.

As for user upload, that shouldn't make a difference. It al depends on how you process the upload.

Back to your question:

I would create an upload form with the action pointing towards the picserver and an ajaxcall from the picserver to the applicationserver with details of the uploaded image.

you would still need 2 CI installations but the picserver only needs a simple upload routine and an ajax call.