As of today Microsoft has announced that they will double the amount of free OneDrive storage of those who have turned on automatic image-upload on their phone.
Originally Microsoft announced this because Apple chose to offer the entry level iPhone with only 16GB of memory.

Microsoft says that the additional free storage will be available for a limited time, so you can better activate the auto-upload sooner than later. You can check if your account got the additional storage by going to onedrive.com.