Icloud backend

Bonjour, me revoici avec un nouveau projet. Description en anglais ci-dessous.

We want to use icloud to store all the images made with an iOS App so that each user of the App will be able to see all images made with this App.

imagine Instagram where all pictures are stored in icloud.
We already have something running but it needs to be enhanced and ported to iCloud:
[URL visible pour les membres Pro]

Knowing that iCloud is somehow a new and a bit fragile technology, we're looking for someone with some background on the subject.

We're ok to invest enough hours of dev time for a proof of concept.
The App takes a picture, stores it in iCloud.
We can then display the images in 3 categories (last, popular, best) and rate them.
We push the App in as many hands as possible and see how it handle the workload.

We're looking for an estimate of budget and time to create and test this proof of concept App.
Merci,
yann.