It depends on how many images you have in the queue, and how many total images are in there.
Generally speaking, approximately 5 images per user will be released each day. If you've loaded dozens of images, it will take several days to "work off the excess inventory". However, if you've only submitted a few images, it's fairly certain that they'll be released the same day, or over the course of one or two days.
By limiting the number of each user's images we release each day, it assures every user a shot at having some of their images appear in the PDB and newsletters. (If we went on a strictly first in/first out basis, we might spend several days releasing only one user's images.)