The following image file types are supported for Photo Stream: JPEG, TIFF, PNG, and RAW.
When importing photos to an iPad using the Camera Connection Kit, photos are saved directly to Camera Roll. If Photo Stream is enabled and you are connected to a wireless network, you could potentially reach any of the limits listed above. To avoid this, disable Photo Stream when importing photos to iPad when using the Camera Connection Kit.
When importing large numbers of photos to either iPhoto or Aperture, you could potentially reach any of the limits listed above if you have selected Automatic Upload in the Photo Stream preferences. Both iPhoto and Aperture will pause uploading to Photo Stream when the maximum has been reached. Uploading will automatically restart at the next hour, day, or month, depending on which limit was reached.
The ever-insightful John Gruber:
“[…] last I heard, significant improvements to Photo Stream were slated as a 2014 thing, not a 2013 thing.”
1000 is fairly a small number for a device like the iPhone 5 & the 5S. I’m guessing the reason why Apple had this limits in the first place was to control scaling on their infrastructure. Now that people has grasped the concept, it’s time for them to lift the limit and make iCloud photo a full-blown feature.