Just wanted to share some of the feedback I provided recently to the Apps Team on the designs, in case any other designer wants to add on something:

The flows (and the later iPhone mockups) look really nice.

Here are some comments:

On Android, the log-in involves an initial choice between "log-in" and "sign-up":

Have you considered to show directly the log-in view (assuming that that is the common case) and provide a secondary action to create account?
Consider using an alternative term for sign-up such as "New account", "Create account" or "Register". The idea is to make it more specific and distinguish more clearly from log-in to avoid confusion. In any case, if the user fails to log-in, options to recover password and create account may be helpful to be provided.

The "adding picture - naming" iteration is really important here since it involves the painful activity of typing in a mobile device. I think it is important to allow uploading as early as possible and don't block the user with the diting step. By looking at the docs it is not completely clear for me how it works:

The "next" button on #7 seems to convey the idea that images should be described sequentially following a specific order. Users may need to correct a spelling mistake, or prefer to copy and paste text for two non-consecutive images. Maybe there you can allow users to move right when going next and move left when going back so that the user can swipe through the images to be edited.
Have you considered a way to cancel a queued upload?
I would expect the name and description not to block the uploading (as it seems to happen when you make a picture with the camera").
You should consider whether to include support for related iterations such as provide facilities for users naming pictures of the same serie. Since this is a commodity user rarely anticipate I don't envision this as a specific options users need to select in advance but some kind of help such as an autocompleting drop-down with previous descriptions if the user starts typing the same.

Show an article once if it is the same in different languages (+ an indicator of the number of languages for which the image is used in) instead of replicating the same content.
I always liked the ide of using images to represent articles instead of generic icons, but I'm not sure if it fits this scenario since the uploaded image may be the same or very similar to the article one.

On iPhone, it is a bit strange for me to use the split buttons on top to switch between sign-up and log-in. Although both actions require similar views I would try not to present it as two views of the same thing.
I like the visual style of the later iPhone mockups. Although content is properly emphasised I would try to make some concepts that reduce the chrome even more.

An idea could be to use the "today" view as "home" where in addition to the tile of recent pictures, some special tiles are used for my uploads and campaigns. these new tiles can be represented as a stack of actual content with an icon and/or label indicating that are yours/campaigns. In this way the bottom menu is no longer needed apart from the main "add picture" action.

The central "add picture" button is really great. It clearly identifies the main action:

You may consider making the targets a bit bigger since those are main actions of the app.
Similarly, you could try to attenuate (make darkish or lightish) the pictures of the background when the camera and gallery sub-menus are added. The idea is to make them more visible in a background that can be full of color.
In addition to tapping twice (first on the "+" button and then at the camera), it would be nice if the second selection could be also done with the same gesture so advanced users can just slide in one or the other direction.

Some icons work really well (add picture, gallery and camera) but others may be a bit unclear although I recognise that they are not easy to solve and probably won't make a big difference:

"my pictures" is a bit indirect (more related to me than to the pictures) but I can understand that we need to differentiate from the gallery. I'm not sure if showing a person inside a picture frame will make things mor clear or generate more confusion, but you could give a try.
The icon for the "today" view is not very clear, but since it is the default view its easy to learn (you may consider a home icon).
The campaign one may work if notification of new campaigns appear. then the echo icon would make sense.

Pau