edjgraphix,
First and foremost, greetings! Long time no hear.

As to your question. From the looks of it they stay put in the database, and can still be viewed by others. I have noticed on occasion while looking at certain images, for the sheer pleasure of it or prior to downloading any that I might need, the word 'Unknown' shows up where it says "uploaded by..." instead of the user's name. I have to assume those are individuals who simply deleted their accounts. I hope that helps.
Cheers,
-Silverfox