Not all of my photos go to Photo Stream, some still go to my Camera Roll. I'm trying to get them on my Photo Stream so they will be on iCloud. With 30 photos on my camera, 10 in stream, I took 6 photos. 2 appeared in stream, 4 did not. Some of my subsequent photos also appeared in the stream, but not all. This is arbitrary behavior by the program. How to fix? Assume ios 7.0.
Any photos that exist in the Camera Roll that didn't come from the device itself had to come from another device. The primary method for getting these pictures into iCloud's 1000 picture buffer is to enroll that other device into iCloud.
You have one case of a picture that was taken either more than 30 days ago or 1000 pictures ago or you deleted your entire Photo Stream and want to start over. In this case, you may need to sync those photos to a computer or another device using the Camera Connecton Kit to inject them into your current Photo Stream.
It's possible the photos you are looking for are in the stream, but just ordered differently than you expected. For example on my iphone I imported some images from mail. Because the pictures had been taken a while ago they were at the top of the stream instead of the bottom, where I expected them to be. The stream orders them by date taken, where as the camera roll orders them by date imported.
You can go to any picture in your Camera Roll, select it and then copy it by pressing the Home button and the Sleep button. This will make a screenshot of the picture in your Camera Roll and send that up to iCloud.
With iOS 6 you can select photos from your camera roll and share them to a personal photo stream to yourself.